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University  of  California  •  Berkeley 


THE  LIBRARY 

OF 
THE  UNIVERSITY 

OF  CALIFORNIA 

PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


.-c\ 


THE     MICROSCOPIST. 


THE 


MICROSCOPIST; 


OB, 


ON  THE 


USE  OF  THE  MICROSCOPE: 


FOB 


PHYSICIANS,  STUDENTS, 


AND  ALL 


LOVEES  OF  NATUKAL  SCIENCE. 


WITH  ILLUSTRATIONS. 


BT 


JOSEPH  H.  WYTHE^  M.D. 


PHILADELPHIA: 

LINDSAY  AND  BLAKISTON. 
1852. 


Entered,  according  to  Act  of  Congress,  in  the  year  1851, 

BY  LINDSAY  AND  BLAKISTON, 
In  the  Clerk's  Office  of  the  District  Court  for  the  Eastern  District  of  Pennsylvania. 


C.   SHERMAN,    PRINTED. 


W 


TO 

PAUL  BECK  GODDARD,  M.D., 

DISTINGUISHED  BY 

HIS  ARDENT  AND  SUCCESSFUL  PROSECUTION 

OP 
THIS  AND  KINDRED  STUDIES, 


IS  RESPECTFULLY  INSCRIBED 
BY 

THE  AUTHOR. 


PREFACE. 


SINCE  the  employment  of  achromatic  instruments,  mi- 
croscopic research  has  ceased  to  be  merely  an  amuse- 
ment, but  has  been  elevated  to  the  dignity  of  a  science ; 
yet,  so  far  as  the  author  knows,  no  book  has  been  issued 
from  the  American  press  which  would  serve  as  a  guide 
to  those  desirous  of  applying  themselves  to  such  studies. 

The  present  work  aims  to  supply  this  deficiency.  In 
its  preparation  the  author  has  aimed  less  at  style  than 
at  information.  Its  matter  has  been  condensed  into  the 
smallest  possible  space,  so  that  it  may  be,  what  its  title 
professes,  "  A  Complete  Manual  on  the  Use  of  the  Micro- 
scope." It  does  not  supersede  the  necessity  of  more 
elaborate  works,  especially  in  the  departments  of  Minute 
Anatomy  and  Pathology,  but  gives  directions  by  which 
such  works  may  be  more  profitably  employed  by  the  stu- 
dent. The  multiplied  labours  of  many  observers  have 
been  classified  and  arranged,  and  free  use  has  been  made 


X  PREFACE. 

of  English  authorities,  so  as  to  bring  the  work  up  to  the 
present  standard  of  information ;  at  the  same  time  the 
opinions  and  experience  of  the  author  have  been  stated 
without  hesitation. 

Respecting  the  construction  of  the  Microscope  itself, 
a  brief  description  is  all  that  was  deemed  necessary ;  nor 
could  it  have  been  much  more  extended  without  being 
liable  to  serious  objection.  As  to  the  employment  of 
the  instrument  upon  the  various  objects  of  science,  as 
full  an  account  has  been  given  as  was  consistent  with 
brevity;  and  to  make  this  department  more  complete, 
reference  has  been  made  to  the  doctrines  and  discoveries 
of  modern  Physiology  and  Pathology. 

The  work  is  committed  to  the  notice  of  the  scientific 
community  with  the  hope  that  it  may  prove  of  service  in 
the  study  of  the  wonderful  works  of  the  Great  Creator, 
who  is  "  all  in  all,  and  all  in  every  part ;"  whose  Power 
and  Wisdom  are  seen  as  well  in  the  minutest  atom  as  in 
the  most  gigantic  masses ;  and  whose  government  em- 
braces not  only  intelligent  free  agents,  but  also  the 
smallest  animalculse  existing  in  a  drop  of  stagnant  water. 


CONTENTS. 


PAGE 

CHAPTER  I.  THE  HISTORY  AND  IMPORTANCE  OF  MICROSCOPIC 

INVESTIGATION,  .  .  .  .13 

II.  THE  MICROSCOPE,     ....  22 

III.  ADJUNCTS  TO  THE  MICROSCOPE,  .  .        40 

IV.  How  TO  USE  THE  MICROSCOPE,         .  .  49 
V.  ON   MOUNTING  AND   PRESERVING   OBJECTS  FOR 

EXAMINATION,              .            .            .  .53 

VI.  ON  PROCURING  OBJECTS  FOR  THE  MICROSCOPE,  64 

VII.  TEST  OBJECTS,    .            .            .            .  .98 

VIII.  ON  DISSECTING  OBJECTS  FOR  THE  MICROSCOPE,  105 

IX.  THE  CELL-DOCTRINE  OF  PHYSIOLOGY,     .  .114 

X.  EXAMINATION  OF  MORBID  STRUCTURES,  ETC.,  124 

XI.  ON  MINUTE  INJECTIONS,               .             .  .134 

XII.  EXAMINATION  OF  URINARY  DEPOSITS,             .  143 

XIII.  ON  POLARIZED  LIGHT,     .            .            .  .162 

XIV.  MISCELLANEOUS  HINTS  TO  MICROSCOPISTS,    .  170 


THE   MICROSCOPIST, 


CHAPTER  I. 

THE    HISTORY    AND    IMPORTANCE    OP    MICROSCOPIC 
INVESTIGATION. 

FROM  the  earliest  period  of  scientific  research,  the  magnify- 
ing properties  of  lenses  have  been  used  to  penetrate  the  arcana 
of  nature,  and  with  most  striking  results.  A  vast  amount  of 
information,  which  could  have  been  obtained  in  no  other  way, 
has  been  added,  by  microscopic  observation,  to  almost  every 
branch  of  natural  science. 

To  the  Christian  philosopher,  the  microscope  reveals  the 
most  amazing  evidence  of  that  Creative  Power  and  Wisdom 
before  which  great  and  small  are  terms  without  meaning.  He 
rises  from  the  contemplation  of  the  minutiae  which  it  displays, 
feeling  more  strongly  than  ever  the  force  of  those  beautiful 
words — "  If  God  so  clothe  the  grass  of  the  field,  which  to-day 
is,  and  to-morrow  is  cast  into  the  oven,  shall  he  not  much  more 
clothe  you?  0  ye  of  little  faith!" 

To  the  geologist,  it  reveals  the  striking,  yet  humbling  fact, 
that  the  world  on  which  we  tread  is  but  the  wreck  of  ancient 

2 


14  THE    MICROSCOPIST. 

organic  creations.  The  large  coal  beds  are  the  ruins  of  a 
luxuriant  and  gigantic  vegetation;  and  the  vast  limestone 
rocks,  which  are  so  abundant  on  the  earth's  surface,  are  the 
catacombs  of  myriads  of  animal  tribes  which  are  too  minute 
to  be  perceived  by  the  unassisted  vision.  It  exhibits,  also, 
that  metallic  ore,  as  the  Bog  Iron  Ore,  and  immense  layers  of 
earthy  and  rocky  matter,  are  formed  merely  by  the  aggregation 
of  the  skeletons  or  shields  of  Infusoria;  while  beds  of  coral 
rocks  are  still  in  the  process  of  formation,  the  architects  being 
tiny  marine  polypi.  Further,  by  this  instrument,  the  nature 
of  gigantic  fossil  remains  is  often  determined,  and  by  it  they 
are  assigned  their  true  place  in  the  classification  of  the 
naturalist. 

To  the  student  of  vegetable  physiology,  the  microscope  is  an 
indispensable  instrument.  By  it  he  is  enabled  to  trace  the 
first  beginnings  of  vegetable  life,  and  the  functions  of  the  dif- 
ferent tissues  and  vessels  in  plants. 

The  zoologist  finds  it  also  a  necessary  auxiliary.  Without 
it,  not  only  would  the  structure  and  functions  of  many  animals 
remain  unknown,  but  the  existence  of  numerous  species  would 
be  undiscovered. 

It  is  to  the  medical  student  and  practitioner,  however,  that 
the  microscope  commends  itself  for  its  utility.  A  new  branch 
of  medical  study — histology — has  been  created  by  its  means 
alone ;  while  its  contributions  to  morbid  anatomy  and  physi- 
ology, or  pathology,  are  indispensable  to  the  student  or  phy- 
sician who  would  excel,  or  even  keep  pace  with  the  progress  of 
others,  in  his  profession.  To  such  the  following  remarks  will 
doubtless  be  interesting. 

Histology  is  that  science  which  treats  of  the  minute  or  ulti- 
mate structure  and  composition  of  the  different  textures  of 
organized  bodies.  It  is  derived  from  Woe:,  a  tissue  or  web,  and 
,  a  discourse. 


HISTORICAL    INVESTIGATION.  15 

The  attempts  made  by  the  early  microscopic  observers  to 
determine  ultimate  structure,  were  in  general  of  little  value, 
partly  on  account  of  the  imperfections  in  the  instruments  em- 
ployed, and  partly  from  the  mistakes  they  made  in  judging  of 
the  novel  appearances  presented  to  their  view.  This  last  cause 
of  error  still  exists,  and  inexperienced  observers  may  very 
readily  be  led  astray.  By  such,  a  fibre  of  cotton  upon  the 
stage  of  the  microscope,  moving  in  obedience  to  the  hygrometric 
influence  of  the  breath  or  of  a  moist  atmosphere,  might  be  re- 
garded as  a  living  animal ;  or  the  influence  of  various  reagents 
on  pus,  mucus,  blood,  or  other  matters,  might  lead  to  error. 
This  last  was  the  case  with  the  celebrated  Borelli,  who  was 
the  first  to  apply  the  microscope  to  the  examination  of  struc- 
ture. 

Borelli  was  born  in  1608,  and  lectured  as  professor  in  the 
University  of  Pisa  in  1656.  In  his  day  a  general  idea  pre- 
vailed, that  diseases  were  occasioned  by  animalculse  existing  in 
the  animal  tissues  and  fluids.  An  examination  of  abnormal 
fluids  with  the  microscope  favoured  this  idea,  as  the  globules 
were  immediately  taken  for  living  beings.  Borelli  described 
the  pus  globules  as  animalcules,  and  even  says  he  has  seen  them 
delivering  their  eggs.  It  will  be  seen  that  this  was  a  very 
natural  mistake,  when  we  remember  that  these  globules  contain 
several  minute  granules,  which  make  their  escape  when  the 
external  envelope  is  broken  or  dissolved.  In  this  way  we 
often  find  the  germs  of  truth  in  the  curious  speculations  of 
the  early  microscopists. 

Malpighi  was  the  first  to  witness  the  most  beautiful  sight 
which  the  microscope  can  reveal, — the  actual  circulation  of  the 
blood,  thereby  demonstrating  the  reasoning  of  Harvey  to  be 
true.  The  first  work  he  published,  in  1661,  comprises  his 
microscopic  observations  relative  to  the  structure  of  the  lungs. 
Between  this  period  and  1665,  he  published  other  tracts  on 


16  THE     MICROSCOPIST. 

the  minute  anatomy  of  the  kidneys,  spleen,  liver,  membranes 
of  the  brain,  &c.,  and  several  of  the  structures  still  retain  his 
name.  He  also  paid  attention  to  the  anatomy  and  transforma- 
tions of  insects,  the  development  of  the  chick  in  the  egg,  and 
the  structure  of  plants.  It  will  be  perceived  from  the  last 
remark,  that  the  intimate  connexion  between  animal  and  vege- 
table physiology  was  even  then  acknowledged.  This  connexion 
has  led  to  the  establishment  of  the  cell  doctrine,  or  the  theory 
of  the  development  of  all  organized  tissues  from  cells. 

Lewenhoeck  has  sometimes  been  called  the  father  of  micro- 
graphy. He  was  born  at  Delft,  in  Holland,  in  1663,  and 
appears  to  have  received  a  rather  indifferent  early  education. 
He  first  brought  himself  into  notice  by  the  skill  with  which 
he  ground  glasses  for  microscopes  and  spectacles,  and  for  im- 
provements in  those  instruments;  thus  affording  a  good  model 
for  microscopic  observers :  first  attending  to  the  optical  and 
mechanical  construction  of  the  instrument  he  was  to  employ.  In 
1690  he  discovered  and  demonstrated  the  capillary  blood-vessels. 
He  opposed  the  chemical  doctrines  which  then  reigned  in  medi- 
cine, which  attributed  disease  to  fermentation  in  the  blood. 
He  objected;  that  if  fermentation  existed,  air  bubbles  would  be 
seen  in  the  vessels,  which  was  not  the  case.  He  showed  that 
the  blood-globules  were  of  different  sizes  and  forms  in  various 
tribes  of  animals,;  examined  the  brain  and  nerves,  the  mus- 
cles, the  crystalline  lens,  the  milk,  and  numerous  other  textures 
and  fluids ;  and  made  the  interesting  discovery  of  the  sperma- 
tozoa, which  he  conceived  to  be  of  different  sexes.  There  can 
be  no  doubt  that  he  made  numerous  errors,  but  the  whole  sub- 
ject being  new,  his  errors  were  excusable;  and  his  contributions 
to  science  are  still  of  the  highest  interest. 

Swainmerdam,  Lyonet,  and  Ellis,  after  this  period,  greatly 
extended  our  knowledge  of  the  lower  tribes  of  animals ;  while 


HISTORICAL    INVESTIGATION.  17 

Lieberkuhn,  Fontana,  and  Hewson  laboured  successfully  in  the 
department  of  histology. 

To  Lieberkuhn  we  owe  the  first  good  account  of  the  anatomy 
of  the  villi,  and  of  the  minute  tubular  glands  of  the  small 
intestine,  which  still  bear  his  name.  As  a  minute  injector  he 
has  never  been  surpassed. 

Fontana  examined  the  brain,  nerves,  muscles,  and  several 
other  textures,  with  great  care,  and  his  observations  were  ex- 
tremely accurate. 

Hewson  is  celebrated  for  his  accurate  observations  on  the 
blood  and  lymph  corpuscles.  He  first  demonstrated  that  the 
blood-globules  were  flat,  with  a  central  nucleus,  and  not  round, 
as  had  been  previously  supposed. 

Nearly  all  the  celebrated  men  alluded  to,  made  use  of  the 
simple  microscope.  At  this  period  the  compound  microscope 
was  very  defective.  It  was  more  of  a  toy  than  a  scientific 
instrument. 

From  an  ignorance  of  many  phenomena  connected  with  the 
microscope  which  are  now  well  understood,  many  errors 
resulted.  Optical  illusions  were  mistaken  for  natural  appear- 
ances, as  was  the  case  with  Monro.  In  his  discoveries  respect- 
ing the  brain  and  nerves,  he  describes  them  as  being  formed 
of  convoluted  fibres,  and  in  his  examination  of  other  textures 
he  saw  the  same  fibres  and  always  mistook  them  for  nerves. 
The  fact  was,  that  he  made  his  observations  while  the  direct 
rays  of  the  sun  were  transmitted  through  the  substance  under 
examination,  and  the  optical  phenomena  which  were  produced 
led  to  the  mistake.  He  afterwards  found  them  on  the  surface 
of  metals,  and  then  frankly  acknowledged  his  error. 

Another  source  of  early  errors  was  the  treatment  to  which 
their  preparations  were  subjected  before  examination.  It  is 
now  well  known  that  animal  tissue  should  be  examined  while 
fresh  and  transparent.  What  result  is  it  possible  to  draw  from 


18  THE    MICROSCOPIST. 

the  observations  of  those  wjio  boil,  roast,  macerate,  putrefy, 
triturate,  and  otherwise  injure  the  delicate  tissues  ?  Most  of 
the  tissues  contain  albumen,  which,  so  treated,  gives  origin  to 
globules,  and  flakes  of  different  forms ;  a  circumstance  which 
has  led  several  anatomists  to  conceive  the  basis  of  animal 
structures  to  be  globular.  Several  late  observers  have  also 
made  this  mistake. 

Messrs.  Todd  and  Bowman,  the  learned  authors  of  "  The 
Physiological  Anatomy  and  Physiology  of  Man,"  present  the 
following  sensible  remarks  respecting  this  subject, — "To  make 
microscopical  observation  really  beneficial  to  physiological 
science,  it  should  be  done  by  those  who  possess  two  requisites : 
an  eye,  which  practice  has  rendered  familiar  with  genuine 
appearances  as  contrasted  with  those  produced  by  the  various 
aberrations  to  which  the  rays  of  light  are  liable  in  their  pas- 
sage through  highly  refracting  media,  and  which  can  quickly 
distinguish  the  fallacious  from  the  real  form;  and  a  mind, 
capable  of  detecting  sources  of  fallacy,  and  of  understanding 
the  changes  which  manipulation,  chemical  reagents,  and  other 
disturbing  causes  may  produce  in  the  arrangement  of  the  ele- 
mentary parts  of  various  textures.  To  these  we  will  add 
another  requisite,  not  more  important  for  microscopical  than 
for  other  inquiries;  namely,  a  freedom  from  preconceived 
views  or  notions  of  particular  forms  of  structure,  and  an  ab- 
sence of  bias  in  favour  of  certain  theories,  or  strained  analogies. 
The  history  of  science  affords  but  too  many  instances  of  the 
baneful  influence  of  the  idola  specfts  upon  the  ablest  minds ; 
and  it  seems  reasonable  to  expect  that  such  creatures  of  the 
fancy  would  be  especially  prone  to  pervert  both  the  bodily  and 
the  mental  vision,  in  a  kind  of  observation  which  is  subject  to 
so  many  causes  of  error,  as  that  conducted  by  the  aid  of  the 
microscope." 

The  invention  of  the  achromatic  object-glasses  for  micro- 


HISTORICAL    INVESTIGATION.  19 

scopes  formed  the  beginning  of  a  new  epoch  in  histological  pur- 
suits. Since  that  period,  the  confusion  and  opposition  which 
formerly  existed  among  observers  have  diminished,  and  at 
present  only  those  differences  remain  which  are  incident  to  the 
pursuit  of  any  other  branch  of  scientific  study. 

In  our  own  times,  the  Germans  seem  to  have  taken  the  lead 
in  histological  observations ;  and  the  reputation  of  the  well- 
known  names  of  Ehrenberg,  Miiller,  Schwann,  Schulz,  Wagner, 
Weber,  and  Valentin,  principally  depends  on  the  discoveries 
they  have  made  by  means  of  the  microscope. 

In  England,  the  names  of  Carpenter,  Todd,  Bowman,  Owen, 
Cooper,  Busk,  Quekett,  Bowerbank,  and  others,  are  connected 
with  microscopic  research. 

In  our  own  country,  a  spirit  of  emulation  seems  excited, 
which  promises  great  advantage.  Professor  Bailey  of  West 
Point,  and  our  townsmen,  Drs.  Leidy  and  Groddard,  may  be 
mentioned  among  others  who  have  contributed  to  this  result. 
The  recent  lectures  of  Dr.  Groadby  (late  minute  dissector  to 
the  Royal  College  of  Surgeons,  England),  on  microscopic 
science,  have  done  much  to  increase  a  desire  on  the  part  of 
medical  students  and  others  to  become  practically  acquainted 
with  this  subject.  His  lectures  to  the  students  of  the  Phila- 
delphia College  of  Medicine,  and  at  other  places,  were  well 
attended ,  as  likewise  were  his  private  classes.  Of  his  valu- 
able suggestions  I  have  frequently  availed  myself. 

The  advantage  of  a  practical  acquaintance  with  the  micro- 
scope by  medical  men  may  be  easily  seen,  and  is  readily 
acknowledged.  Dr.  Bennet,  of  Edinburgh,  to  whom  I  am 
indebted  for  much  of  the  histological  part  of  this  introduction, 
says — "I  have  lately  had  many  opportunities  of  satisfying 
myself  that  death  may  be  occasioned  by  structural  changes  in 
the  brain,  which  are  altogether  imperceptible  to  ordinary  vision, 
and  which  have  escaped  the  careful  scrutiny  of  the  first  morbid 


20  THE    MICROSCOPIST. 

anatomists  in  this  city.  Again,  who  would  have  imagined  that 
porrigo  favosa,  mentagra,  aphtha,  and  other  diseases,  consist  of 
cryptogamous  plants  growing  on  the  skin  or  mucous  mem- 
branes? Surely  facts  like  these  hold  out  a  strong  inducement 
to  the  histologist  who  prosecutes  pathological  inquiries."  In 
another  place  he  relates  the  following  circumstance,  which  tends 
to  illustrate  the  same  point:  " A  gentleman  who  had  an  ab- 
scess in  the  arm,  observed  one  morning  his  urine  to  be  turbid, 
and  to  deposit  a  considerable  sediment.  The  practitioner  who 
attended  him  thought  it  looked  like  purulent  matter,  but  before 
finally  forming  his  diagnosis,  he  asked  me  to  examine  it  with 
the  microscope.  I  did  so ;  but  instead  of  finding  pus  corpus- 
cles, discovered  a  large  quantity  of  irregularly  formed  granules, 
which  I  recognised  to  be  fibrinous.  I  immediately  suggested 
that  the  abscess  was  on  the  point  of  resolution,  and  I  after- 
wards learned,  that  from  that  time  it  rapidly  disappeared. 
The  fact  that  fibrin,  exuded  into  the  tissues,  and,  subsequently 
absorbed,  passes  off  by  the  kidneys,  was  determined  by  the 
microscopic  observations  of  Schbnlein  and  Zimmerman  in  Ger- 
many." 

Many  other  instances  might  be  adduced,  were  it  necessary, 
to  show  the  importance  of  the  microscope  in  diagnosis  and  in 
practical  medicine.  It  is  not  too  much  to  hazard  the  assertion, 
that  in  a  few  years'  the  practitioner  will  find  it  as  essential  in 
finding  out  the  nature  of  disease,  and  the  state  of  the  system, 
as  the  most  valuable  articles  of  the  materia  medica  are  useful 
in  medical  treatment.  The  following  example  will  illustrate 
the  delicacy  as  well  as  utility  of  this  mode  of  investigation. 
A  few  evenings  since,  while  entertaining  a  friend  with  some 
microscopic  views,  he  expressed  a  wish  to  see  the  red  globules 
of  the  blood;  so,  pricking  the  tip  of  his  finger  with  a  lancet,  a 
drop  was  extracted,  which,  after  covering  with  thin  glass,  was 
placed  upon  the  stage  of  the  microscope.  Observing  the  glo- 


HISTORICAL    INVESTIGATION.  21 

bules,  with  a  greater  tendency  than  usual,  to  run  together  into 
rows,  like  piles  of  coin,  I  remarked  to  him,  that  his  blood 
assumed  an  inflammatory  or  a  feverish  appearance.  He  replied, 
that  he  had  been  for  about  thirty-eight  hours  without  sleep, 
having  sat  up  with  a  sick  friend  the  night  before,  and  having 
some  gastric  irritation  in  addition,  he  had  felt  feverish  all  the 
evening.  Observations  on  pus,  mucus,  the  urine,  and  the 
various  forms  of  malignant  tumours,  &c.,  all  exhibit  the  value 
of  this  instrument  to  medical  science. 

In  medico-legal  researches  the  microscope  has  already  proved 
a  valuable  auxiliary.  It  has  several  times  been  employed  to 
ascertain  the  true  nature  of  spots  suspected  to  be  blood-stains, 
&c. ;  and  in  cases  where  human  life  was  suspended  upon  its 
decision. 

In  1837,  M.  Ollivier  was  directed  to  ascertain  whether  any 
human  hair  was  attached  to  the  blade  of  a  hatchet  seized  in 
the  house  of  a  person  suspected  of  murder,  and  if  this  were 
the  case,  to  determine  the  colour  of  the  hair.  With  the  micro- 
scope, M.  Ollivier  ascertained  that  the  filaments  attached  to 
the  hatchet  were  the  hairs  of  an  animal,  and  not  of  a  human 
being ;  and  this  was  afterwards  fully  proved. 


CHAPTER   II. 


THE  MICROSCOPE. 

THOSE  who  have  examined  a  common  magnifying  glass  (or 
lens)  know  that  it  is  necessary  to  hold  it  exactly  at  a  certain 
distance  from  the  object  viewed  through  it,  in  order  that  such 
object  may  be  seen  with  distinctness.  The  point  at  which  the 
object  must  be  placed  is  called  the  focus  of  the  lens,  and  the 
distance  from  the  middle  of  the  lens  to  the  focus  is  the  focal 
length,  or  focal  distance  of  the  lens. 

The  cut  represents  sections  of  the  different  forms  of  lenses. 
A,  is  a  plano-convex  lens.  B,  double  convex.  C,  plano-con- 
cave. D;  double  concave.  E;  a  meniscus. 


Fig.  1. 
C 


The  effect  of  the  convex  lens  or  of  the  meniscus  is  to  cause 
the  rays  of  light  which  pass  from  any  object  through  them,  to 
converge  towards  a  point  or  focus ;  and  the  eye  receiving  those 


THE    MICROSCOPE.  23 

rays  after  passing  through  the  lens,  sees  the  object  apparently 
magnified.  This  principle  is  the  basis  upon  which  all  micro- 
scopes are  constructed. 

The  concave  lens  produces  a  precisely  contrary  effect  to  that 
described  above.  The  rays  of  light  diverge  on  passing  through 
it,  and  the  object  appears  diminished  in  size. 


SIMPLE    MICROSCOPES. 

A  piano  or  double  convex  lens,  especially  when  mounted,  or 
arranged  with  conveniences  for  viewing  objects,  is  called  a 
simple  microscope. 

The  magnifying  power  of  a  simple  microscope  is  in  propor- 
tion to  the  shortness  of  its  focal  length.  Thus,  a  lens  of  2 
inches  focal  distance,  magnifies  5  diameters  (or  the  superficies 
25  times) — of  1  inch  focus,  10  diameters — fths  of  an  inch,  15 
diameters — £  inch,  20  diameters — \  inch,  40  diameters — ith 
inch,  80  diameters — y^th  inch,  100  diameters. 

This  table  of  magnifying  powers  is  not  invariably  correct, 
owing  to  the  difference  of  vision  in  different  individuals,  but  it 
is  sufficient  for  all  practical  purposes. 

Simple  microscopes  are  mounted  in  a  variety  of  ways,  ac- 
cording to  the  purposes  for  which  they  are  intended.  Some 
are  made  to  turn  upon  a  hinge  into  a  case,  so  as  to  carry  in  the 
pocket  j  and  others  are  fixed  on  a  handle,  with  a  pin  or  small 
pair  of  forceps  in  the  focus,  on  which  a  small  object,  as  an 
insect,  &c.,  may  be  placed. 

The  cut,  Fig.  2,  exhibits  the  arrangement  of  Dr.  Withering' s 
Botanical  Microscope,  which  is  valuable  from  its  simplicity. 
It  consists  of  three  brass  plates,  a,  6,  c,  parallel  with  each  other, 


24  THE    MICROSCOPIST. 

to  the  upper  and  lower  of  which  the  stout  wires,  d,  e,  are  rivet- 
ted.  The  middle  plate,  b,  which  forms  the  stage  for  carrying 
the  objects,  is  made  to  slide  up  and  down  on  these  wires.  The 
upper  plate,  <z,  carries  the  lenses,  i,  and  the  lower  one,  c,  some- 
times carries  a  mirror,  for  reflecting  the  light  of  a  candle  or  of 
the  sky  through  any  transparent  object  which  may  be  placed 
on  the  stage.  Into  the  stage  a  dissecting  knife,  A,  a  pointed 


instrument,  /,  and  a  pair  of  forceps,  #,  are  made  to  fit,  and  can 
be  readily  taken  out  for  use  by  sliding  the  stage  down  nearly 
to  the  mirror. 

A  very  useful  kind  of  simple  microscope  was  that  invented 
by  Mr.  Wilson ;  an  early  form  of  which  is  represented  by  Fig. 
3.  The  body,  A,  A,  A,  A,  which  was  made  either  of  ivory,  brass, 
or  silver,  was  cylindrical,  and  about  two  inches  in  length,  and 
one  inch  in  diameter.  Into  the  lower  end,  B,  the  magnifiers 
are  screwed,  and  into  the  upper  end  screws  a  piece  of  tube,  D, 
carrying  at  the  end,  C,  a  convex  glass,  and  on  its  outside  a 
male  screw.  Three  thin  plates  of  brass,  E,  are  made  to  slide 


THE     MICROSCOPE. 


25 


easily  in  the  inside  of  the  body  to  form  the  stage.  One  of 
these  plates,  F,  is  bent  semicircular ly  in  the  middle,  for  the 
reception  of  a  tube  of  glass,  for  viewing  the  circulation  of  the 


Fig.  3. 


blood  in  small  fish,  while  the  other  two  are  flat,  and  between 
these  last  the  object-sliders,  K,  are  introduced.  Between  the 
stage  and  the  end  of  the  body,  B,  is  a  bent  spring  of  wire,  H; 
to  keep  the  stage  and  object  steadily  against  the  screw-tube. 
The  object  is  adjusted  to  the  focus  by  turning  the  screw  D. 
This  instrument  was  held  in  the  hand  in  such  a  position  that 
the  light  of  a  lamp  or  candle  might  pass  directly  into  the  con- 

3 


26 


THE    MICROSCOPIST. 


densing  glass.     It  was  afterwards  improved  by  the  addition  of 
a  handle  placed  at  right  angles  to  its  body. 

The  best  form  of  the  simple  microscope  for  viewing  opaque 


Fig.  4. 


objects,  is  that  represented  by  Fig.  4  :  a  is  a  flat  piece  of  brass 
attached  to  the  handle,  p  ;  it  supports  the  lens-holder,  i,  and 
through  it  passes  the  screw,  Z>,  which  is  connected  to  the  back- 
plate,  c;  a  spring,  e,  keeps  the  plates,  a,  c,  apart,  and  the  nut, 


THE    MICROSCOPE. 


27 


d,  adjusts  the  lens  to  the  focus  of  the  object,  either  on  g  or  h. 
But  the  chief  merit  in  its  construction  consists  in  a  concave 
speculum  or  mirror  of  silver,  k,  highly  polished,  to  the  centre 
of  which,  at  ?,  the  magnifying  glass  is  adapted.  This  is  screwed 
into  the  ring  it  and  so  held  that  a  bright  light,  as  from  a  can- 
dle or  white  cloud,  is  received  upon  the  speculum  (called  a 
Lieberkuhn,  from  the  name  of  its  inventor).  The  light  so 
received  is  concentrated  upon  the  object,  which  is  brightly 
illuminated;  and  is  adjusted  to  the  focus  of  the  lens  by  turn- 
ing the  nut  d. 

For  minute  dissection  of  animal  or  other  tissues,  which  is 
generally  performed  under  water,  as  hereafter  described,  the 


microscope  of  Mr.  Slack,  with  the  improvements  of  Dr.  H. 
Goadby,  F.L.S.,  is  the  most  efficient.  The  following  is  a  de- 
scription of  the  instrument  employed  by  the  latter  gentleman 
in  his  microscopic  researches;  and  with  which  he  has  made  a 


28  THE    MICROSCOPIST. 

great  number  of  beautiful  preparations  in  minute  anatomy, 
entomology,  &c.  It  consists  of  a  box  or  case,  which  is  repre- 
sented by  A,  Fig.  5.  The  upper  surfaces  r,  r,  are  sloped  off  to 
form  arm-rests.  The  front  of  the  case  (which  is  not  seen  in 
the  cut)  is  furnished  with  a  flap  or  door,  which  has  hinges  at 
the  bottom  and  a  lock  at  the  top ;  so  that  the  various  parts  of 
the  instrument  may  be  packed  up  inside. 

In  the  top  of  the  box  is  a  round  hole,  B,  into  which  fits  the 
short  piece  of  tube  attached  to  the  tin  box,  C,  which  is  de- 
signed to  hold  the  water  in  which  the  dissection  is  made.  The 
ring,  D,  is  the  lens-holder,  which  is  adjusted  to  the  proper 
focus  by  means  of  the  milled  head,  E,  which  moves  the  rack, 
F,  up  and  down,  working  inside  the  box  A.  The  lens-holder 
has  also  a  horizontal  motion,  by  means  of  the  rack  and  pinion, 
Gr.  Another  horizontal  motion  is  produced  by  a  swivel  joint 
attached  to  F.  Inside  the  box  is  a  mirror,  directly  under  the 
hole  B,  so  that  the  light  can  be  directed  upwards  through  any 
transparent  object  at  B. 

When  moderate  power  only  is  needed,  a  simple  microscope 
is  the  best  instrument  which  can  be  used ;  and  for  the  purpose 
of  making  minute  dissections  it  is  also  the  most  convenient ; 
but  when  a  very  high  magnifying  power  is  needed,  combined 
with  distinctness  of  observation,  a  single  (or  simple)  micro- 
scope is  found  to  be  imperfect :  although  very  small  lenses 
have  been  made,  which  magnify  exceedingly — quite  enough 
for  all  useful  purposes.  Grood  lenses,  of  a  high  magnifying 
power,  may  be  made  by  drawing  out  a  very  narrow  strip  of 
glass  in  the  flame  of  a  spirit  lamp,  and  upon  the  end  of  the 
thread  thus  formed,  running  a  small  globule  by  means  of  the 
flame,  which  may  be  detached  from  its  thread  and  placed  be- 
tween two  thin  plates  of  metal  in  which  a  small  hole  has  been 
drilled. 


THE     MICROSCOPE. 


29 


Optical  Improvements  in  the  Simple  Microscope. — There 
are  imperfections  of  vision  attending  the  use  of  all  com- 
mon lenses;  arising  either  from  the  shape  of  the  lens,  or 
from  the  nature  of  light  itself  when  passing  through  a  refract- 
ing medium.  These  imperfections  are  termed  respectively, 
spherical  and  chromatic  aberrations.  To  lessen  or  destroy  these 
aberrations  various  plans  have  been  proposed,  with  various 
success.  Mr.  Coddington  proposed  a  lens  in  the  form  of  a 
sphere,  cut  away  round  the  centre,  as  at  A,  Fig.  6.  This  is 
an  excellent  form  for  a  hand  lens,  but  is  not  often  to  be  pro- 
cured in  this  country;  opticians  preferring  to  dispose  of  the 


Stanhope  lens,  seen  at  B,  which  is  more  easily  made  than  the 
Coddington  lens,  but  is  inferior  to  it.  C  and  D  are  doublets 
proposed  by  Sir  John  Herschell ;  the  first  of  which  consists  of 
two  plano-convex  lenses,  a,  b}  whose  focal  lengths  are  as  2-3 
to  1,  with  their  convex  sides  together ;  the  least  convex  next 
the  eye,  D,  consists  of  a  double  convex  lens,  a,  next  the  eye, 
and  a  meniscus,  5.  When  these  lenses  are  used  for  forming 
images  the  lenses  marked  a  should  be  next  the  object. 

Other  forms  of  doublets  have  been  proposed,  but  by  far  the 


30 


THE     MICROSCOPIST. 


best  arrangement  of  this  kind  is  Dr.  Wollaston's  Doublet, 
which  consists  of  two  plano-convex  lenses,  whose  focal  lengths 
are  as  1  to  3 ;  the  plane  sides  of  each,  and  the  smallest  lens, 
placed  towards  the  object.  The  lenses  are  set  in  separate  cells 
so  as  to  adjust  their  proper  distance  apart,  which  is  best  done 
by  experimenting  on  their  performance,  although  their  dis- 
tance is  about  the  difference  of  their  focal  lengths.  Between 
them  is  a  diaphragm  or  stop,  generally  placed  immediately 


Fig.  7. 


behind  the  anterior  lens.     The  stop  was  not  employed  by  Dr. 
Wollaston,  as  his  lenses  were  of  such  high  power  that  they 


THE    MICROSCOPE.  31 

nearly  touched  each  other;  yet  it  is,  nevertheless,  found  to  be 
essential  to  a  good  doublet. 

A,  C,  Fig.  7,  represent  the  lenses  of  the  doublet,  and  B  is 
the  diaphragm  or  stop.  The  manner  in  which  the  light  is 
refracted  by  this  instrument,  is  shown  by  the  lines  proceeding 
from  each  end  of  the  object,  0.  The  dotted  lines  represent 
the  blue  or  most  refrangible  rays  of  the  spectrum;  the  others 
are  the  red  rays.  Those  rays  which  pass  through  the  centre 
of  the  lens,  A,  are  caused  to  pass  through  the  hole  in  the  dia- 
phragm over  to  the  margin  of  B,  and  those  nearest  the  margin 
of  A  pass  next  the  centre  of  B ;  and  so  become  nearly  cor- 
rected :  the  imperfection  of  one  being  made  to  counteract  that 
of  the  other. 

An  improvement  was  made  upon  this  by  Mr.  Holland,  and 
is  called  Holland's  Triplet.  It  consists  of  a  doublet  in  place 
of  the  first  lens,  A,  in  the  last  figure ;  retaining  the  stop  be- 
tween it  and  the  lens  C.  This  form  is  the  highest  stage  of 
perfection  which  the  simple  microscope  has  ever  yet  attained. 
The  great  objection  to  its  use,  however,  is,  that  it  must  be 
brought  into  such  close  proximity  to  the  object,  that  it  is  im- 
possible to  cover  such  object  except  with  the  thinnest  mica, 
which  is  objectionable  on  account  of  its  liability  to  be 
scratched. 

Before  dismissing  the  subject  of  single  microscopes,  it  may 
be  well  to  remark,  that  for  a  low  magnifying  power,  a  double 
convex  lens  is  the  best  to  use ;  but  for  medium  or  high  powers, 
a  plano-convex  lens,  with  the  convex  side  towards  the  object ; 
or  one  of  the  doublets  just  described ;  is  preferable. 

THE    COMPOUND     MICROSCOPE 

Consists  essentially  of  two  convex  lenses ;  an  object-glass  and 
an  eye-glass;  as  represented  in  Fig.  8. 


32 


THE    MICROSCOPIST. 


A  is  the  object-glass,  which  forms  a  magnified  image  of  the 
object  at  C,  which  is  further  enlarged  by  the  eye-glass  B.    An 


Fig.  8. 


A 


additional  lens,  I),  is  usually  added ;  for  the  purpose  of  en- 


THE    MICROSCOPE.  33 

larging  the  field  of  view.  It  is  called  the  field-lens.  An 
inspection  of  the  dotted  lines  in  the  figure  will  show  that  many 
of  the  rays  pass  beyond  the  reach  of  the  eye-glass,  B :  an 
image  from  these  rays  is  represented  at  E.  These  rays  are 
intercepted  by  the  field-glass  D,  and  form  an  image  at  F,  which 
is  viewed  by  the  eye-glass. 

In  looking  through  a  common  microscope  of  this  kind,  the 
observer  will  probably  see  rings  of  colour  round  the  edge  of 
the  field  of  view,  and  also  similar  colours  around  the  edges  of 
the  object  he  is  viewing.  These  defects  arise  from  the  decom- 
position of  common  white  light;  and  are  called  chromatic 
aberration  or  dispersion.  The  colours  round  the  field  of  view 
are  produced  by  the  defects  of  the  eye-piece ;  and  those  round 
the  object,  by  the  object-glass.  Again :  if  the  object  be 
looked  at  through  the  instrument  as  before,  its  outline  or 
edges  will  be  observed,  not  sharp  and  distinct,  but  thick  and 
confused.  This  is  caused  by  the  rays  not  being  collected  into 
a  perfect  point  as  they  were  on  the  object  itself.  This  defect 
is  called  spherical  aberration.  When  an  instrument  has 
neither  its  chromatic  nor  spherical  aberration  removed,  it  is 
said  to  be  uncorrected. 

To  conceal  these  defects  there  is  generally  a  small  hole  or 
stop  behind  the  object-glass.  This  is  injurious  to  correct 
vision,  as  it  prevents  a  large  portion  of  light  from  entering  the 
eye,  and  makes  the  objects  appear  dark,  so  that  their  true 
structure  cannot  be  made  out.  When  this  is  the  case,  the 
instrument  is  said  to  want  angular  aperture.  The  stop  refer- 
red to,  however,  is  essential  even  to  the  moderate  performance 
of  a  common  instrument. 

To  obviate  all  these  difficulties,  improvements  have  been  made 
both  in  the  object-glasses  and  the  eye-pieces.  Wollaston's 
Doublet  has  been  found  capable,  when  used  as  an  object-glass 
with  the  Huygenian  eye-piece  (hereafter  described),  of  trans- 


34  THE    MICROSCOPIST. 

mitting  a  large  pencil  of  light  with  great  distinctness,  having 
an  angular  aperture  of  from  35°  to  50°.  Mr.  Holland's 
Triplet,  used  in  the  same  way,  is  capable  of  transmitting  a 
pencil  of  65°  with  distinctness  and  correctness  of  definition. 
The  achromatic  object-glasses,  as  first  proposed  by  Mr.  Lister, 
have  however  superseded  all  other  attempts  to  improve  the 
compound  microscope,  and  have  raised  it  from  the  condition  of 
a  mere  toy,  to  be  the  most  valuable  instrument  of  scientific 
research.  They  are  made  of  plano-concave  flint,  and  double- 
convex  crown  glass  lenses,  cemented  together.  Three  com- 
pound lenses  form  the  object-glass  for  a  microscope,  as  repre- 
sented by  Fig.  9,  a,  b,  c.  In  object-glasses  of  a  high  power, 


Fig.  9. 


the  anterior  compound  lens,  a,  has  sometimes  an  adjustment  to 
render  it  suitable  for  objects  either  uncovered  or  covered  with 
glass  of  various 'thickness.  The  object-glass,  thus  made,  is  not 
quite  achromatic,  being  rather  over-corrected  as  to  colour,  but 
is  finally  corrected  by  using  the  Huygenian  eye-piece,  shown  in 
Fig.  10. 

This  eye-piece  consists  of  two  plano-convex  lenses,  A,  B,  with 
their  plane  sides  next  the  eye.  In  the  focus  of  A  is  the  dia- 
phragm or  stop,  C.  The  proportions  of  the  focal  lengths  of 
these  lenses  should  be  as  3  to  1,  and  their  distance  apart,  one- 
half  the  sum  of  their  focal  distances.  Thus,  if  B  be  three 


THE     MICROSCOPE.  35 

inches  focus,  A  should  be  one  inch,  and  their  distance  apart 
two  inches. 


Sometimes,  when  a  very  flat  field  of  view  is  required,  as  in 
the  use  of  a  micrometer  eye-piece,  the  convex  sides  of  the 
lenses  face  each  other.  It  is  recommended  that  for  this  kind 
of  eye-piece  the  lenses  should  be  nearly  of  the  same  focal 
length,  and  at  a  distance  equal  to  two-thirds  the  focal  length  of 
either. 

A  good  compound  microscope  should  be  furnished  with 
many  mechanical  conveniences,  in  addition  to  the  optical  part 
just  described.  It  should  be  capable  of  being  steady  in  any 
position  from  vertical  to  horizontal — have  coarse  and  fine  ad- 
justments for  focus — have  a  large  and  firm  stage,  with  ledge, 
clips,  &c.;  and  with  traversing  motions,  so  as  to  follow  an 
object  quickly,  or  readily  bring  it  into  the  field  of  view, — and 
should  have  a  concave  and  plane  mirror,  of  two  inches  diame- 
ter, with  a  universal  joint,  and  capable  of  being  brought  nearer 
or  farther  from  the  stage,  as  likewise  of  reflecting  a  side-light. 

A  variety  of  forms  have  been  given  to  the  mechanism  of  the 


36  THE    MICROSCOPIST. 

compound  microscope,  many  of  which  are  very  good,  while 
others  are  exceedingly  objectionable.  Suffice  it  to  say  respect- 
ing them,  that  steadiness,  or  freedom  from  vibration,  and 
particularly  freedom  from  any  vibrations  which  are  not  equally 
communicated  to  the  object  under  examination  and  to  the 
lenses  by  which  it  is  viewed,  is  a  point  of  the  utmost  conse- 
quence. A  microscope  body  containing  the  lenses,  screwed  by 
its  lower  extremity  to  a  horizontal  arm,  is  the  worst  form  con- 
ceivable. 

The  most  celebrated  artists  in  the  manufacture  of  these 
instruments  are  Powell  and  Lealand;  Ross;  and  Smith  and 
Beck,  of  London.  A  microscope  from  the  latter  firm  is  repre- 
sented in  the  frontispiece. 

The  body  slides  by  a  rack  and  pinion,  moved  by  the  milled- 
head,  a,  on  a  strong  dovetailed  bar ;  and  has  also  a  slow  mo- 
tion for  delicate  adjustment  of  focus,  given  by  the  milled-head 
b.  It  is  furnished  with  a  sliding  tube,  c,  for  varying  its  length ; 
and  with  three  sliding  Huygenian  eye-pieces,  d,  d',  d",  of 
successive  powers. 

The  erecting  glasses,  ^,  are  to  be  screwed,  when  employed, 
into  the  other  end  of  the  sliding  tube.  They  rectify  the 
image,  which  is  inverted  when  seen  in  the  usual  way.  Their 
chief  advantage  is  in  microscopic  dissection. 

The  stage  has  two  steady  rackwork  motions,  at  right  angles 
to  each  other  and  to  the  axis  of  the  body,  given  by  the  milled- 
heads,  e,  e' ;  it  has  also  a  sliding  and  revolving  plane,  /,  with 
a  ledge,  g,  for  resting  object-slips  upon,  and  a  sliding-piece,  h, 
with  springs  for  clamping  them.  An  upright  rod,  iy  is  fixed 
on  this  plane  for  mounting  the  forceps,  v,  or  for  the  spring- 
holder,  /,  when  a  glass  trough,  u,  is  used.  A  profile  of  the 
glass  trough,  with  its  diagonal  plate  of  glass  for  confining  an 
object,  is  seen  at  u'.  At  z,  is  a  three-pronged  forceps. 

A  large  double  mirror,  k,  concave  on  one  side  and  plane  on 


THE    MICROSCOPE.  37 

the  other,  is  supported  by  the  cylindrical  bar,  l}  and  may  be 
moved  upon  it  vertically  and  sideways. 

A  movable  diaphragm,  m,  is  fixed  under  the  stage  for  vary- 
ing the  quantity  and  direction  of  the  light  when  transparent 
objects  are  viewed.  The  illuminating  lens,  n,  is  used  for  con- 
densing light  upon  opaque  objects ;  and  a  silver  side-reflector 
is  for  the  same  purpose.  The  bull's-eye  lens,  for  increasing  the 
illumination,  is  seen  at  r. 

An  achromatic  condenser,  x,  slides  into  the  place  of  the 
diaphragm,  to  give  the  utmost  refinement  to  the  illumination  of 
transparent  objects. 

The  live-box,  s,  is  for  observing  living  objects  between  two 
glass  plates ;  and  a  second  live-box,  s',  with  screw  collar,  for 
objects  in  water.  The  screw  is  for  regulating  the  depth  of 
water,  and  the  degree  of  pressure  employed. 

A  plate  of  glass,  t,  with  a  ledge,  has  a  separate  piece  of  thin 
glass  to  lie  upon  it,  for  viewing  animalcules,  &c.,  in  water. 

The  camera  lucida,  w,  has  its  prism  fixed  on  a  short  tube 
with  a  slight  side  motion  for  adjustment,  and  fits  on  each  eye- 
piece when  its  cap  is  removed. 

The  three  Lieberkuhns,  o,  o',  o",  adapted  to  the  object- 
glasses  2,  3,  and  4,  are  applied  by  sliding  them  in  front  of 
each  respectively.  When  one  of  these  is  used,  the  diaphragm 
is  to  be  removed,  and  the  dovetailed  piece,  p,  may  be  slid  in  its 
place,  with  one  of  the  three  dark  wells  or  stops,  p}  p',  p"}  which 
will  make  a  dark  background.  If  the  objects  are  mounted  on 
circular  discs,  (7,  the  well  will  not  be  needed. 

The  object-glasses  comprise  four  powers.  No.  8  and  No.  4 
have  the  tube  of  their  front  lens  movable  for  adjusting  their 
performance  with  objects  either  uncovered  or  covered  with  thin 
glass.  The  graduated  screw  collar,  by  which  the  adjustment  is 
made,  is  seen  at  5. 

The  high  price  of  these  instruments  must  necessarily  put 

4 


38  THE     MICROSCOPIST. 

them  out  of  the  reach  of  those  whose  means  are  limited,  and 
our  opticians  seldom  import  them,  except  to  order.  Of  late, 
however,  a  praiseworthy  effort  has  been  made  to  simplify  the 
construction  of  the  mechanical  parts,  so  as  to  bring  the  price 
within  the  control  of  the  generality  of  medical  men  and  other 
students  of  nature.  Mr.  J.  B.  Dancer,  Manchester,  England, 
furnishes  a  very  complete  microscope,  with  two  object-glasses 
and  the  necessary  apparatus,  for  £10.  Messrs.  Powell  and 
Lealand  have  also  fitted  up  an  instrument  with  a  stand  of  cast- 
iron,  whose  cost,  exclusive  of  the  object-glasses,  is  £9.  Other 
manufacturers  are  also  pursuing  the  same  course. 

From  the  cause  above  referred  to,  the  majority  of  micro- 
scopes used  in  this  country  are  of  French  or  German  manufac- 
ture. Chevalier  and  Oberhauser  have  furnished  some  excellent 
instruments;  but  the  construction  of  most  of  those  used  or 
exposed  for  sale,  is  far  inferior  to  the  English.  Hitherto,  also, 
the  fashion  in  this  country  in  regard  to  microscopes,  has  led 
to  the  almost  universal  employment  of  high  powers,  to  the 
neglect  of  the  others,  so  that  it  is  exceedingly  difficult  to  pro- 
cure an  achromatic  object-glass  with  shallow  magnifiers,  not- 
withstanding the  decided  advantage  to  be  derived  from  their 
use. 


REFLECTING    MICROSCOPES 


In  which  the  image  was  formed  by  a  concave  mirror  instead 
of  a  lens,  are  not  now  so  much  used  as  formerly.  They  are 
generally  complicated  in  structure,  and  are  surpassed  and 
therefore  superseded  by  the  achromatic  microscope. 

The  following  is  a  simple  reflecting  microscope,  invented  by 
Mr.  S.  Gray,  and  may  be  of  some  interest  from  its  singularity. 

A,  Fig.  11,  represents  a  brass  ring,  one-thirtieth  of  an  inch 
thick,  whose  inner  diameter  is  about  two-fifths  of  an  inch. 


THE    MICROSCOPE. 


39 


Having  dissolved  a  globule  of  quicksilver  in  one  part  nitric 
acid  and  ten  parts  water,  he  rubbed  with  it  the  inner  surface 


of  the  ring,  which  became  silvered ;  having  wiped  it  dry,  he 
put  a  drop  of  quicksilver  within  it,  which,  when  pressed  with 
the  finger,  adhered  to  the  ring,  and  formed  a  convex  speculum. 
When  the  ring  was  taken  up  carefully,  and  laid  on  the  margin 
of  the  cylinder,  B,  the  mercury  sank  down,  and  formed  a 
concave  reflecting  speculum.  The  cylinder,  B,  is  supported  by 
a  pillar,  which  is  attached  to  the  foot,  D.  The  stage,  Gr,  is 
for  holding  the  object,  and  is  adjusted  to  the  focus  by  the  screw 
atC. 


CHAPTER   III. 


ADJUNCTS    TO    THE    MICROSCOPE. 


IN  addition  to  the  mirror,  object-glasses,  eye-glasses,  and 
the  parts  constituting  the  stand  of  a  microscope,  several  acces- 
sory instruments  are  needed  by  those  who  would  devote  atten- 
tion to  microscopic  researches.  The  most  necessary  or  useful 
of  these  we  proceed  to  describe. 

The  Diaphragm,   for   cutting   off  extraneous   light   when 

Fig.  12. 


viewing  minute  transparent  objects,  consists  of  a  plate  of  brass 
perforated  with  several  holes  of  different  sizes.  This  revolves 
on  a  pivot,  so  as  to  bring  each  hole  in  succession  under  the 
object-glass.  It  is  adapted  under  the  stage  of  the  instrument, 
and  is  so  essential  in  practice  that  few  microscopes  are  made 
without  it. 

The  Condenser. — This  is  an  arrangement  under  the  stage 


ADJUNCTS    TO    THE    MICROSCOPE.  41 

for  condensing  the  light  upon  the  object.  The  best  instruments 
employ  an  arrangement  of  achromatic  glasses,  similar  to  the 
object-glasses,  but  its  value  is  scarcely  equal  to  its  cost.  The 
Wollaston  Condenser  is  a  short  tube,  in  which  a  plano-convex 
lens  of  three-fourths  of  an  inch  focal  length,  with  its  flat  side 
towards  the  object,  is  made  to  slide  up  and  down.  Dr.  Wollas- 
ton employed  a  long  tube  with  a  stop  between  the  lens  and  the 
mirror,  but  Dr.  Groring  found  it  better  to  have  the  stop  be- 
tween the  lens  and  the  object,  and  a  little  out  of  the  axis  of 
the  lens. 

A  substitute  for  the  achromatic  condenser  is  found  in  Mr. 
Varley's  dark  chamber.  This  is  sometimes  preferable  to  the 
"Wollaston  Condenser,  as  the  light  is  not  decomposed  by  pass- 
ing through  a  lens. 

c,  Fig.  13,  is  a  plate  of  brass  adapted  to  the  stage,  in  which 
is  a  short  tube  having  a  diaphragm  or  stop,  a,  whose  aperture 


is  equal  to  what  can  be  viewed  by  the  microscope  and  no 
larger.  Below  is  a  sliding  tube,  6,  with  an  aperture  rather 
larger  than  that  at  a.  This  last  can  be  moved  up  and  down 
until  the  light  at  a  is  of  the  greatest  intensity.  The  aperture 
at  a  is  always  in  proportion  to  the  object-glass  employed. 

Polarizing  Apparatus,  (Fig.  14,)  for  viewing  objects  by 
polarized  light.  It  consists  usually  of  two  prisms  of  calca- 
reous spar,  in  proper  tubes ;  one  below  the  stage,  and  the 
other  in  the  eye-piece.  Sometimes  a  thin  piece  of  tourmaline 
is  used  in  place  of  the  prism  in  the  eye-piece. 


42 


THE    MICROSCOPIST. 


Erector. — This  is  sometimes  supplied  with  the  best  instru- 
ments. It  consists  of  a  pair  of  lenses  acting  like  the  erecting 
eye-piece  of  the  telescope.  It  is  applied  to  the  draw  tube  at 

Fig.  14. 


the  end  of  the  eye-piece  towards  the  object-glass.  It  is  only 
used  when  it  is  desired  to  dissect  with  the  compound  micro- 
scope, as,  without  it,  the  position  of  the  object  appears  re- 
versed. 

Condensing  Lens  and  Lamp. — The  Wollaston  Condenser, 
&c.,  is  designed  to  concentrate  the  light  which  comes  from  the 
mirror,  directly  upon  the  object;  but  the  condensing  lens  and 
lamp  is  used  either  for  opaque  objects,  or  to  condense  the  light 
upon  the  mirror  itself.  Two  such  lenses,  as  in  the  figure,  are 
generally  used.  Dr.  G-oadby  informed  me,  that  after  many 
experiments  he  has  found  a  bull's-eye  lens,  of  three  inches 
focal  length,  the  most  efficient  for  the  larger  lens;  and  after 
several  trials  with  different  sorts  of  lenses  I  am  disposed  to 
agree  with  him.  Fig.  15  illustrates  one  mode  of  using  the 
condensers  upon  opaque  objects..  A,  is  the  bull's-eye  lens, 


ADJUNCTS    TO    THE     MICROSCOPE. 


43 


which  turns  upon  its  axis,  and  slides  up  and  down  a  stout  wire 
affixed  to  a  steady  foot.     B,  is  the  smaller  lens,  whose  handle 


Fig.  15. 


slides  through  a  socket,  working  on  a  hinge  joint.  Sometimes 
a  lens  of  this  kind  is  affixed  to  the  stage  of  the  microscope. 
C,  is  the  object  upon  which  the  light  is  concentrated.  D,  the 
lamp.  To  condense  the  light  on  the  mirror,  the  lens,  A,  alone 
is  used.  The  lamp  is  of  the  kind  called  a  fountain  lamp,  and 
slides  up  and  down  a  stem,  on  which  it  can  be  fixed  at  any 
height  by  the  screw  F.  E  represents  a  section  of  a  shade, 
which  should  always  be  used  with  the  lamp.  As  it  is  a  matter 


44 


THE     MICROSCOPIST. 


of  much  consequence  to  our  observations  that  we  should  have 
a  steady,  intense  light,  it  is  not  immaterial  what  kind  of  oil, 
&c.,  we  employ.  After  many  trials  and  disappointments,  I  am 
convinced  that  pure  sperm  oil  is  the  pleasantest,  cheapest,  and 
best. 

Lielerkuhn,  or  Silver  Cup. — This  is  a  most  useful  instru- 
ment for  viewing  opaque  objects.  It  is  attached  to  the  object- 
glass  in  the  manner  represented  by  Fig.  16,  where  a  is  the 
lower  end  of  the  body  of  the  microscope,  b  the  object-glass, 


Fig.  16. 


to  which  the  Uieberkuhn,  c,  is  attached.  The  rays  of  light 
reflected  from  the  mirror,  are  brought  into  a  focus  upon  an 
object,  dj  mounted  in  the  usual  way  upon  glass,  or  held  in 
the  forceps,  f.  When  the  object  is  transparent,  or  is  too  small  to 
fill  up  the  entire  field  of  view,  the  dark  well  or  stop,  e,  is  used. 
This  is  generally  fixed  into  the  centre  of  the  stage,  a  little 
below  the  upper  surface.  Sometimes,  instead  of  a  Lieberkuhn, 
a  side-reflector  is  used,  and  from  the  greater  obliquity  of  its 
reflection,  is  of  great  advantage  in  exhibiting  delicate  struc- 
tures. 


ADJUNCTS    TO    THE    MICROSCOPE.  45 

It  has  hitherto  been  considered  impracticable  to  use  very 
high  powers  with  opaque  objects,  but  the  Athenaeum  informs 
us  that  "  at  one  of  Lord  Rosse's  recent  scientific  soirees,  Mr. 
Brooke  showed  his  new  method  of  viewing  opaque  objects 
under  the  highest  powers  of  the  microscope  (the  ith  and  ^th 
inch  object-glasses).  This  is  performed  by  two  reflections. 
The  rays  from  a  lamp,  rendered  parallel  by  a  condensing  lens, 
are  received  on  an  elliptic  reflector,  the  end  of  which  is  cut  off 
a  little  beyond  the  focus ;  the  rays  of  light  converging  from 
this  surface  are  reflected  down  on  the  object  by  a  plain  mirror 
attached  to  the  object-glass,  and  on  a  level  with  the  outer  sur- 
face. By  these  means  the  structure  of  the  scale  of  the  podura, 
and  the  different  characters  of  the  inner  and  outer  surfaces,  are 
rendered  distinctly  visible."  I  have  not  had  an  opportunity 
of  testing  this  plan,  but  have  little  doubt  of  its  success. 

Camera  Lucida. — By  which  drawings  are  made  from  the 
microscope.  This  is  generally  formed  by  placing  a  small  prism 
of  glass,  inclined  at  the  proper  angle,  in  front  of  the  eye-piece. 
In  Fig.  17,  a,  represents  the  camera,  formed  of  highly-polished 

Fig.  17. 


steel,  smaller  than  the  pupil  of  the  eye,  inclined  at  an  angle 
of  45°,  and*fixed  to  a  clip,  6,  which  embraces  the  eye-piece. 


46 


THE    MICROSCOPIST. 


Frog-plate;  Fig.  18;  on  which  frogs  or  fish  are  tied  to  ex- 
amine the  circulation  of  blood  in  their  vessels.     The  frog,  &c., 


Fig.  18. 


must  first  be  enclosed  in  a  bag,  and  fastened  on  the  plate  by 
the  holes  in  either  side  of  it.  Then  thread  is  tied  to  about 
four  of  its  toes,  and  the  web  is  spread  out  over  the  large  hole 
by  fastening  the  ends  of  the  thread  through  the  smaller  holes 
in  the  plate. 

The  Stage  Micrometer  consists  of  a  slip  of  glass,  pearl,  &c., 
having  a  line  finely  divided  into  parts  of  an  inch,  &c.  To 
obtain  with  this  the  power  of  a  compound  microscope,  compare 
the  divisions  seen  with  one  eye  through  the  instrument,  with 
a  rule  held  ten  inches  off,  and  looked  at  with  the  other  eye. 
Suppose,  for  instance,  the  micrometer  be  divided  into  youths 
of  an  inch,  and  one  of  these  divisions  covers  an  inch  of  the 
rule  seen  with  the  other  eye,  the  magnifying  power  of  the 
instrument  is  100  diameters.  If'  it  should  cover^ve  inches, 


ADJUNCTS    TO     THE     MICROSCOPE.  47 

it  is  magnified  500  diameters.     By  sketching  the  object  by 
means  of  the  camera,  and  then  putting  in  its  place  a  stage 


Fig.  20. 


micrometer,  and  marking  the  divisions  over  the  sketch,  they 
can  again  be  subdivided,  and  so  the  measure  of  an  object 
be  accurately  taken. 


48  THE     MICROSCOPIST. 

Animalculse  Cage  is  a  round  cell  with  a  glass  bottom  and 
top,  for  confining  a  drop  of  water  with  animalculse. 

Watch-Glasses  and  Fishing  Tubes,  are  useful  adjuncts.  The 
latter,  Fig.  19,  are  glass  tubes  of  various  sizes,  by  which  when 
one  end  is  closed  with  the  finger  a  quantity  of  water,  &c.,  may 
be  lifted  from  a  phial,  as  seen  at  Fig.  20,  and  put  in  a  watch- 
glass.  By  their  aid,  too,  with  a  little  practice,  an  animalcula 
may  be  caught  in  a  phial,  when  it  is  visible  to  the  naked  eye. 
With  the  finger  on  one  end  of  the  tube,  approach  the  other 
end  to  the  place  where  the  animal  is,  then  suddenly  lifting  off 
the  finger,  the  current  will  carry  it  into  the  tube. 

A  Compressorium,  for  applying  pressure  to  an  object;  a 
trough  for  chara  and  polypi;  &  phial-holder,  &c. ;  will  also  be 
found  useful. 


CHAPTER   IV. 


HOW    TO    USE    THE    MICROSCOPE. 

MANY  persons  imagine  that  the  value  of  a  microscope  is  in 
proportion  to  the  apparent  size  of  an  object  seen  through  it. 
This,  however,  is  a  mistake.  The  greater  the  magnifying 
power  of  an  instrument,  all  other  things  being  equal,  the 
greater  is  the  difficulty  of  finding  a  minute  object  on  the  stage, 
and  of  adjusting  the  focus.  The  light,  too,  transmitted  from 
the  mirror,  becomes  less  intense,  and  the  view  less  satisfactory 
with  the  use  of  high  powers.  For  the  majority  of  objects,  a 
low  or  medium  power  is  always  preferable,  on  account  of  the 
greater  extent  of  the  field  of  view.  The  test  objects,  however, 
and  the  minute  structure  of  any  delicate  tissue,  &c.,  require 
very  considerable  amplification  in  order  to  exhibit  them  satis- 
factorily. When  this  is  the  case,  the  increase  of  power  should 
be  given  by  the  employment  of  an  object-glass  of  shorter  focal 
length,  in  preference  to  the  use  of  a  more  powerful  eye-piece. 

Sir  David  Brewster  gives  the  following  rules  for  microscopic 
observations. 

1.  The  eye  should  be  protected  from  all  extraneous  light, 
and  should  not  receive  any  of  the  light  which  proceeds  from 
the  illuminating  centre,  excepting  what  is  transmitted  through 
or  reflected  from  the  object. — This  rule  will  illustrate  the  use 
of  the  diaphragm  under  the  stage  of  the  microscope. 

5 


50  THE    MICROSCOPIST. 

2.  Delicate  observations  should  not  be  made  when  the  fluid 
which  lubricates  the  cornea  of  the  eye  is  in  a  viscid  state. 

3.  The  best  position  for  microscopic  observations  is  when 
the  observer  is  lying  horizontally  on  his  back.     This  arises 
from  the  perfect  stability  of  the  head,  and  from  the  equality 
of  the  lubricating  film  of  fluid  which  covers  the  cornea.     The 
worst  of  all  positions  is  that  in  which  we  look  downwards  ver- 
tically.    The  most  common  and  easy  position  is  generally  with 
the  instrument  inclined  at  an  angle  of  45  degrees. 

4.  If  we  stand  straight  up  and  look  horizontally,  parallel 
markings  or  lines  will  be  seen  most  perfectly  when  their  direc- 
tion is  vertical;  viz.,  the  direction  in  which  the  lubricating 
fluid  descends  over  the  cornea. 

5.  Every  part  of  the  object  should  be  excluded,  except  that 
which  is  under  immediate  observation. 

6.  The  light  which  illuminates  the  object  should  have  a 
very  small  diameter.     In  the  day-time  it  should  be  a  single 
hole  in  the  window  shutter  of  a  darkened  room,  and  at  night 
an  aperture  placed  before  an  Argand  lamp. 

7.  In  all  cases,  particularly  when  high  powers  are  used,  the 
natural  diameter  of  the  illuminating  light  should  be  dimi- 
nished, and  its  intensity  increased,  by  optical  contrivances. 

The  following  remarks  by  Mr.  James  Smith,  copied  from 
the  Microscopic  Journal,  vol.  i.,  are  recommended  to  the  con- 
sideration of  all  who  are  in  the  habit  of  using  microscopes. 
"Much  of  the  beauty  of  the  objects  seen  depends  upon  the 
management  of  the  light  that  is  thrown  upon  or  behind  them; 
which  can  only  be  fully  mastered  by  practice.  It  may  be 
remarked,  however,  as  a  general  rule,  that  in  viewing  those 
which  are  transparent,  the  plane  mirror  is  most  suitable  for 
bright  daylight;  the  concave  for  a  lamp  or  candle,  which 
should  have  the  bull's-eye  lens,  when  that  is  used,  so  close  to 
it  that  the  rays  may  fall  nearly  parallel  on  the  mirror.  If  the 


HOW    TO    USE    THE    MICROSCOPE.  51 

bull's-eye  lens  is  not  used,  the  illuminating  body  should  not 
be  more  than  five  or  six  inches  from  the  mirror.  The  latter 
is  seldom  required  to  be  more  than  three  inches  from  the 
object,  the  details  of  which  are  usually  best  shown  when  the 
rays  from  the  mirror  fall  upon  it  before  crossing,  and  the 
centre  should  (especially  by  lamp-light)  be  in  the  axis  of  the 
microscope.  For  obscure  objects,  seen  by  transmitted  light, 
and  for  outline,  a  full  central  illumination  is  commonly  best ; 
but  for  seeing  delicate  lines,  like  those  on  the  scales  of  insects, 
it  should  be  made  to  fall  obliquely,  and  in  a  direction  at  right 
angles  to  the  lines  to  be  viewed. 

"  The  diaphragm  is  often  of  great  use  in  modifying  the  light, 
and  stopping  such  rays  as  would  confuse  the  image  (especially 
with  low  or  moderate  powers),  but  many  cases  occur  when  the 
effects  desired  are  best  produced  by  admitting  the  whole  from 
the  mirror. 

"  If  an  achromatic  condenser  is  employed  instead  of  the  dia- 
phragm, its  axis  should  correspond  with  that  of  the  body ;  and 
its  glasses,  when  adjusted  to  their  right  place,  should  show  the 
image  of  the  source  of  artificial  light,  or,  by  day,  that  of  a 
cloud  or  window  bar  in  the  field  of  the  microscope,  while  the 
object  to  be  viewed  is  in  focus. 

"  The  most  pleasing  light  for  objects  in  general,  is  that  re- 
flected from  a  white  cloud  on  a  sunny  day ;  but  an  Argand's 
lamp  or  wax  candle  with  the  bull's-eye  lens  is  a  good  substi- 
tute. 

"  A  large  proportion  of  opaque  objects  are  seen  perfectly  well 
(especially  by  daylight)  with  the  side  reflector,  and  the  dark 
box  as  a  background;  and  for  showing  irregularities  of  sur- 
face, this  lateral  light  is  sometimes  the  best;  but  the  more 
vertical  illumination  of  the  Lieberkuhn  is  usually  preferable, 
the  light  thrown  up  to  it  from  the  mirror  below  being,  with 
good  management,  susceptible  of  much  command  and  variety." 


52  THE    MICROSCOPIST. 

The  management  of  the  light  with  opaque  objects  must 
depend  in  a  great  degree  upon  their  size,  and  the  manner  in 
which  they  are  mounted.  If  the  object  is  small,  and  so  mount- 
ed as  not  to  intercept  much  of  the  light  from  the  mirror,  the 
mode  illustrated  by  Fig.  16  is  the  best ;  in  other  cases,  that 
shown  in  Fig.  15  is  preferable. 

Next  to  the  proper  illumination  of  the  object,  the  adjust- 
ment of  the  focus  is  the  most  important  thing  to  be  attended 
to.  With  a  low  power,  the  coarse  adjustment  is  usually  suffi- 
cient if  the  workmanship  be  good ;  but  with  a  high  power  it 
becomes  necessary  to  resort  to  the  more  delicate  arrangement 
of  the  fine  adjustment.  Great  care  must  be  taken,  however, 
lest  the  glass  on  which  the  object  is  mounted  be  broken,  or 
the  object-glass  injured,  by  too  sudden  or  too  close  a  contact. 


CHAPTER  V. 

ON   MOUNTING   AND    PRESERVING   OBJECTS   FOR 
EXAMINATION. 

IF  a  low  power  is  used,  and  the  object  be  one  not  necessary 
to  be  preserved,  it  can  be  well  seen  if  placed  in  the  forceps  or 
on  a  slip  of  glass,  but  if  it  be  desired  to  keep  it  for  future 
examination,  some  method  of  preserving  it  from  decay,  dust, 
&c.,  must  be  resorted  to ;  and  the  method  will  vary  according 
to  the  nature  of  the  object. 

TRANSPARENT   OBJECTS. 

Transparent  objects  are  mounted  on  slips  of  glass,  the  size 
of  which,  as  adopted  by  the  Microscopic  Society  of  London,  is 
3  inches  by  1  inch,  or  3  inches  by  1£  inches.  The  French 
opticians,  however,  prepare  many  of  their  slides  2J  inches  by 
|ths  of  an  inch,  and  this  size  is  most  frequently  imported  into 
the  United  States ;  indeed,  a  larger  size  is  unsuitable  for  many 
of  the  French  instruments,  although  to  be  preferred  on  other 
accounts. 

There  are  three  methods  of  mounting  transparent  objects. 
1st,  in  the  dry  way — in  which  the  object  is  simply  placed 
upon  the  slip  of  glass,  and  covered  with  a  thin  glass  cover, 
cemented  by  its  edges  to  the  under  piece,  with  sealing-wax 
varnish,  &c. 

5* 


54  THE    MICROSCOPIST. 

2dly.  In  some  preservative  fluid. 

3dly.  In  Canada  balsam. 

The  glass  slides  should  be  clear,  free  from  veins  and  bub- 
bles, of  uniform  length  and  breadth,  and  should  have  their 
edges  ground  smooth  by  rubbing  them  on  a  flat  cast-iron  plate 
with  emery  and  water. 

Sections  of  teeth  and  bone,  and  of  some  kinds  of  wood, 
hairs  of  animals,  scales  of  butterflies,  test  objects  from  the 
infusoria,  &c.,  are  best  mounted  dry;  but  all  very  delicate 
animal  and  vegetable  tissues,  to  exhibit  their  structure  clearly, 
should  not  be  mounted  in  the  dry  way,  nor  in  Canada  balsam, 
but  in  some  preservative  fluid. 

PRESERVING  FLUIDS. — A  very  considerable  number  have 
been  recommended  by  different  observers.  A  mixture  of  salt 
and  water  was  used  by  Dr.  Cook  for  this  purpose ;  there  is  an 
objection  to  it,  however,  owing  to  the  development  of  a  con- 
fervoid  vegetable. 

Mr.  J.  T.  Cooper,  some  years  since,  made  some  experiments 
with  a  view  to  determine  the  best  fluid  for  preserving  vegetable 
coloured  tissues,  such  as  some  of  the  smaller  fungi,  and  found 
that  salt  and  water,  5  grains  to  the  ounce  of  water,  to  which 
acetic  acid  had  been  added,  answered  very  well.  A  few  drops 
of  creosote  or  of  camphor  will  prevent  the  growth  of  confervas. 

One  part  alcohol  to  5  of  distilled  water — 1  ounce  to  4  of 
water — will  preserve  even  very  delicate  colours.  This  is  the 
basis  of  the  Gannal  process  for  preserving  animal  structures. 
There  is,  however,  the  same  objection  to  the  use  of  this  fluid 
as  to  the  salt  and  water. 

A  weak  solution  of  chromic  acid  is  a  good  preserving  fluid. 

Pure  glycerine  is  prepared  by  the  London  opticians  as  a 
preservative  fluid,  and  is  used  in  the  proportion  of  1  part  to  2 
of  water.  Its  oily  nature,  however,  often  causes  much  diffi- 
culty in  cementing  the  thin  glass  cover  upon  it. 


MOUNTING    AND    PRESERVING    OBJECTS.  55 

Dr.  G-oadby  has  devoted  much  attention  to  this  subject,  and 
has  succeeded  in  supplying  to  the  microscopist  a  ready,  cheap, 
and  effectual  means  for  mounting  animal  structures  with  the 
greatest  possible  ease  and  security.  Dr.  Gr.  received  a  gold 
medal  from  the  Society  of  Arts  for  his  invention.  He  has 
kindly  furnished  me  with  the  following  description  of  his 
different  preserving  fluids. 

"A  1.    Bay  salt  (coarse  sea-salt),  4  ounces, 
Alum,  2  ounces, 
Corrosive  sublimate,  2  grains, 
Boiling  water,  1  quart. 

"  A  2.    Bay  salt,  4  ounces, 
Alum,  2  ounces, 
Corrosive  sublimate,  4  grains, 
Boiling  water,  2  quarts. 

"  The  A  1  fluid  is  too  strong  for  most  purposes,  and  is  only 
to  be  employed  where  great  astringency  is  required  to  give 
form  and  support  to  delicate  structures. 

"  The  A  2  fluid  may  be  very  extensively  used,  and  is  best 
adapted  for  permanent  preparations ;  but  neither  of  these  fluids 
should  be  used  in  the  preservation  of  animals  possessing  any 
carbonate  of  lime  (all  the  Mollusca),  as  the  alum  becomes  de- 
composed, and  the  sulphate  of  lime  is  formed  and  precipitated, 
and  the  animal  spoiled.  For  such  use  the 

"B.  fluid,  specific  gravity  1-100. 

Bay  salt,  8  ounces, 
Corrosive  sublimate,  2  grains, 
Water,  1  quart. 

"  Marine  animals  require  a  stronger  fluid  of  this  kind,  viz., 
specific  gravity  1-148,  which  is  made  by  adding  more  salt 
(about  2  ounces)  to  the  above. 

"  The  corrosive  sublimate  is  used  to  prevent  vegetation  grow- 


56  THE    MICROSCOPIST. 

ing  in  the  fluid,  and  no  greater  quantity  should  be  used  than 
2  grains  per  quart  of  fluid ;  but,  as  it  coagulates  albumen,  it 
must  be  left  out  when  ova  are  to  be  preserved,  or  when  it  is 
desired  to  maintain  the  transparency  of  certain  tissues." 

A  paragraph  has  recently  been  published  in  the  newspapers, 
to  the  effect,  that  "  a  couple  of  French  savans  have  simulta- 
neously discovered  that  chloroform  is  an  antiseptic  of  marvel- 
lous virtue,  preventing  animal  decomposition  after  death,  or 
promptly  checking  it  if  already  commenced.  All  animal 
tissues  when  subjected  to  its  action  become  fixed  for  a  long 
period  of  time  in  the  precise  form  and  condition  in  which  they 
may  happen  to  be  at  the  moment  of  application,  and  natural 
colours,  even  to  the  slightest  and  most  delicate  shades,  are 
preserved  without  the  slightest  change/'  If  this  be  so,  the 
desideratum  in  this  respect  will  be  supplied.  I  have  not  had 
an  opportunity  of  testing  it,  but  look  upon  it  as  quite  pro- 
bable.* 

*  Since  the  above  was  written,  the  following  extract,  confirming 
the  alleged  discovery,  appeared  in  the  Medical  Examiner: — "M. 
Augend  has  communicated  to  the  French  Academy  of  Sciences  the 
following  experiments,  which  establish  a  marked  line  of  demarcation 
between  ether  and  chloroform,  and  point  out  in  the  latter  a  remark- 
able property  which  has  hitherto  escaped  the  attention  of  chemists. 

"  If  three  wide-mouthed,  ground-stoppered  bottles  are  taken,  and 
into  one  we  put  a  few  drops  of  ether,  into  another  a  few  drops  of 
chloroform,  and  leave  the  third  in  statu  quo;  then  place  in  each  a 
piece  of  beef,  secure  the  stoppers,  and  leave  them  during  summer 
weather,  the  following  phenomena  are  observed: — The  flesh,  natural- 
ly of  a  reddish-brown  colour,  passes  at  once  to  a  vermilion-red,  under 
the  influence  of  the  vapour  of  chloroform  mixed  with  air,  whilst  it 
undergoes  no  change  in  the  ether.  Such  are  the  immediate  effects, 
but  at  the  end  of  a  week  the  results  are  still  more  distinct.  The 
flesh  preserved  in  the  air  has  changed  its  colour  slightly,  that  which 
is  preserved  in  the  ether  has  become  brown,  whilst  that  in  the  chlo- 
roform has  acquired  the  appearance  of  boiled  meat.  On  opening  the 
bottles,  the  meat  in  the  air  has  become  offensively  putrid,  and  the 


MOUNTING    AND    PRESERVING    OBJECTS.  57 

MOUNTING  IN  FLUID. — The  most  minute  structures,  such  as 
the  vessels  of  plants,  and  the  muscular  and  other  tissues  of 
animals,  requiring  in  all  cases  high  powers  for  their  proper 
exhibition,  must  of  necessity  be  preserved  in  very  thin  cells 
with  a  small  amount  of  fluid. 

On  a  slip  of  glass,  3  inches  by  1,  cleaned  by  a  solution  of 
caustic  potash  to  remove  all  grease,  lay  a  drop  of  the  fluid ; 
put  the  object  in  this  and  spread  it  out  with  the  point  of  a 
needle,  &c.  Select  a  thin  and  flat  glass  cover,  clear  it  likewise 
from  grease,  &c.,  touch  its  edges  with  cement,  and  drop  it 
gently  over  the  object.  Press  it  lightly,  to  exclude  the  excess 
of  fluid,  which  can  be  removed  by  strips  of  blotting-paper. 
Then  cement  the  edges  of  the  cover  to  the  bottom  glass.  Care 
must  be  taken  to  exclude  all  air-bubbles  from  between  the 
glasses.  Objects  mounted  thus  do  not  keep  long,  and  it  is 

same  thing  occurs  in  the  presence  of  the  ether,  whilst  there  is  no 
change  in  the  flesh  kept  in  the  chloroform,  apart  from  the  sweet  taste 
and  peculiar  odour  of  the  latter. 

"  These  antiseptic  properties  of  chloroform  have  furnished  interest- 
ing results  to  M.  Augend.  He  has  found  that  1 -2000th  part  of  it  (?) 
suffices  to  preserve  a  mass  of  muscular  flesh.  Not  less  remarkable 
is  the  facility  with  which  the  vapour  permeates  the  densest  tissues. 
Chloroform  has  this  advantage  over  creosote,  that  it  does  not  coagu- 
late the  albumen ;  nor  is  it  on  its  part  decomposed  by  muscular 
fibre. 

"  The  most  apparent  action  of  the  chloroform,  not  only  on  muscu- 
lar substance,  but  also  on  the  fleshy  pericarps  of  fruits  and  seeds,  is 
an  immediate  contraction  of  the  fibre  or  the  parenchyma,  which 
causes  the  watery  juices  to  flow  out  on  the  bottom  of  the  vessel  in 
which  the  experiment  is  made. — Gazette  Medicate." 

From  the  foregoing  account,  it  would  seem  proper  to  expose  many 
delicate  tissues  to  the  vapour  of  the  chloroform  before  mounting  in 
balsam ;  or  they  may  be  preserved  in  the  chloroform  itself,  although 
it  would  be  difficult,  in  such  case,  to  find  a  proper  cement  for  the 
glass  cover. 


58  THE    MICROSCOPIST. 

best  io  make  a  thicker  cell.  This  may  be  made  by  painting  a 
round  or  square  ring  on  the  slip  with  some  sort  of  cement 
which  will  not  be  acted  upon  by  the  fluid  employed. — White 
lead  worked  with  1  part  linseed  oil  and  3  of  spirits  of  turpen- 
tine is  well  adapted  for  this  purpose. — In  this  ring,  the  fluid 
and  object  are  placed  and  the  cover  put  on. 

Pieces  are  also  cut  off  the  ends  of  glass  tubes  and  cemented 
on  the  slips  with  marine  glue,  so  as  to  form  very  neat  cells.  A 
square  piece  of  glass,  with  a  hole  drilled  in  it,  cemented  on 
the  slip,  forms  an  excellent  cell.  Such  cells,  ready  prepared, 
are  imported  and  kept  by  McAllister  &  Co.,  Chestnut  Street 
above  Second,  Philadelphia ;  together  with  slips,  thin  glass  for 
covers,  mounted  preparations,  a  good  variety  of  instruments 
themselves,  and  other  things  interesting  or  useful  to  the  micro- 


Pieces  of  gutta  percha  tubes,  cemented  on  to  the  slips  by 
heat,  may  sometimes  be  used  for  cells,  and  answer  a  good  pur- 
pose. I  have  made  excellent  cells  by  using  narrow  slips  of 
glass  for  the  sides,  cementing  them  with  marine  glue.  They 
are  square,  and  are  well  suited  for  the  larger  class  of  objects. 

CEMENTS. 

Japanners'  'Gold-size,  or  Severe  Dryer,  is  a  mixture  of  boiled 
linseed  oil,  dry  red  lead,  litharge,  copperas,  gum  animi,  and 
turpentine.  The  first  and  last  ingredients  are  its  principal 
constituents.  Mr.  Williams,  Artists'  Furnishing  Store,  Sixth 
Street  above  Market,  Philadelphia,  has  it  for  sale. 

Sealing-wax  Varnish  consists  of  small  pieces  of  sealing-wax 
dissolved  in  alcohol. 

Asphaltum,  dissolved  in  turpentine,  has  this  advantage, 
that  spirit  may  be  employed  as  the  preserving,  fluid  if  desired. 

Marine  Glue  is  a  mixture  of  shell-lac,  caoutchouc,  and  naph- 


MOUNTING    AND    PRESERVING    OBJECTS.  59 

tha.  It  is  melted  by  heat.  Caustic  potash  will  remove  its 
traces  from  glass. 

Gum  Mastich  and  Caoutchouc,  dissolved  in  chloroform,  is  an 
excellent  cement,  and  has  the  advantage  of  remaining  fluid  at 
ordinary  temperatures,  while  the  rapid  evaporation  of  the 
chloroform  enables  the  slide  to  be  quickly  prepared. 

A  solution  of  Canada  balsam  in  ether  or  turpentine,  evapo- 
rated to  such  a  consistence  that  it  can  be  laid  on  with  a  camel' s- 
hair  pencil,  may  be  used  like  the  last  described,  as  a  substitute 
for  marine  glue. 

Lampblack  and  white  hard  varnish,  when  laid  on  imme- 
diately, is  a  good  cement.  Sealing-wax  and  white  lead  have 
also  been  recommended. 

For  the  thin  glass  covers,  a  mixture  of  the  gum  mastich 
cement,  above  described,  with  asphaltum  dissolved  in  turpen- 
tine, will  be  found  very  suitable. 


MOUNTING   IN   BALSAM. 

Before  objects  are  mounted  in  Canada  balsam  they  should 
be  perfectly  clean  and  free  from  moisture.  They  are  commonly 
soaked  in  turpentine,  especially  opaque  objects,  as  it  renders 
them  more  transparent.  Grease  may  be  removed  by  sulphuric 
ether. 

Very  thin  and  transparent  objects  become  indistinct  in  bal- 
sam ;  they  should  be  made  dark.  Vegetable  matters  may  be 
charred  between  two  plates  of  glass  over  a  lamp.  Other 
structures  which  cannot  be  charred,  may  be  dyed  by  soaking 
in  a  decoction  of  fustic  or  logwood,  or  a  weak  tincture  of 
iodine. 

The  balsam  should  be  warmed  on  the  slide  to  expel  the  air. 
When  objects  of  a  cellular  nature  have  to  be  mounted,  if  they 
are  such  as  heat  will  not  much  injure,  they  may  be  boiled  in  the 


60  THE     MICROSCOPIST. 

balsam ;  otherwise  numbers  of  air-bubbles  will  be  left  in  the 
cells,  and  the  true  structure  cannot  then  be  made  out  satisfac- 
torily. The  extra  degree  of  heat  will  expand  the  air  and 
cause  it  to  escape,  and  the  balsam  will  take  its  place. 

Some  objects  of  a  tubular  nature,  such  as  the  tracheae  of 
insects,  are  better  seen  if  air  be  contained  in  the  tubes ;  they 
will  then  exhibit  the  spiral  fibre  in  their  interior;  but  a  tra- 
cheal  tube  filled  with  balsam  does  not  show  the  fibre  at  all,  the 
balsam  having  made  all  the  parts  transparent.  Small  insects, 
such  as  fleas,  and  the  parasites  of  animals,  when  not  over- 
heated, show  the  ramifications  of  the  trachea,  but  those  which 
have  been  soaked  long  in  turpentine,  or  have  had  the  air  ex- 
pelled by  heat,  do  not  exhibit  the  spiral  markings  except  under 
polarized  light. 

When  air  is  to  be  got  rid  of,  the  heat  must  be  high ;  other- 
wise, the  use  of  turpentine  must  be  avoided,  the  heat  of  the 
balsam  kept  low,  and  the  mounting  accomplished  quickly. 

The  best  way  to  heat  the  balsam  on  the  slide  is  to  place  the 
slide  on  a  flat  piece  of  iron,  over  a  spirit-lamp ;  yet  with  careful 
management  a  spirit-lamp  will  do  alone. 

Some  persons  keep  their  balsam  in  a  tin  vessel  that  can  be 
warmed  so  as  to  melt  it.  A  drop  of  the  fluid  can  then  be 
taken  out  and  put  on  the  object  upon  the  slide.  This  plan  is 
attended  with  little  or  no  risk  of  air-bubbles.  The  cover 
should  be  warmed  on  its  under  surface  before  it  is  laid  on 
the  balsam,  and  if  necessary,  a  small  amount  of  heat  applied 
to  the  under  side  of  the  slide,  to  make  the  balsam  flow  more 
readily. 

When  animal  structures,  such  as  parts  of  insects,  or  injec- 
tions, have  to  be  mounted,  the  heating  of  the  balsam  must  be 
carefully  managed,  and  the  balsam  itself  be  very  fluid  to  com- 
mence with.  It  should  be  sufficiently  warmed  to  expel  all  air- 
bubbles,  and,  when  nearly  cold, 'the  object  should  be  placed 


MOUNTING    AND    PRESERVING    OBJECTS.  61 

in  it  and  covered  in  the  usual  way.  By  pursuing  this  plan 
(for  which,  with  many  other  suggestions,  I  ain  indebted  to 
Mr.  Quekett's  admirable  work  on  the  Microscope),  I  have  suc- 
ceeded in  making  some  excellent  preparations  at  the  expense  of 
but  little  time  and  trouble. 

If  the  heat  applied  to  the  slide  be  great,  the  object  will  be 
sure  to  curl  up,  and  bubbles  will  appear  in  all  parts.  It  will 
most  likely  be  rendered  useless,  as  no  manipulation,  however 
carefully  applied,  will  restore  an  overheated  specimen  of  ani- 
mal structure  to  its  former  beauty. 

MOUNTING  IN   THE   DRY   WAY. 

For  objects  which  require  a  high  magnifying  power,  they 
may  be  placed  on  a  slide  and  covered  with  thin  glass,  whose 
edges  may  be  touched  with  cement.  Objects  which  do  not 
require  an  object-glass  of  short  focus,  may  be  placed  between 
two  slips  of  glass  whose  edges  have  been  levelled  so  as  to  form 
a  groove,  which  may  be  filled  up  with  cement  or  sealing-wax. 

MOUNTING   OPAQUE   OBJECTS. 

These  must  necessarily  be  viewed  by  light  reflected  in  some 
manner  from  their  surface.  Some  transparent  objects,  however, 
may  be  viewed  as  opaque  ones  by  using  the  dark  well  or  stop, 
e,  Fig.  16.  When  mounted  with  this  design  they  may  be 
placed  on  the  slip  of  glass  with  a  little  gum-water,  and  sur- 
rounded with  a  rim  of  card,  paper,  &c.,  sufficiently  thick  to 
form  a  proper  cell,  which  may  be  covered  with  thin  glass. 
Sometimes  opaque  objects  are  fixed  on  a  round  piece  of  black 
paper  stuck  upon  a  slide. 

a,  Fig.  21,  represents  a  disc  of  leather,  felt,  or  other  suitable 
material,  about  three-eighths  or  half  an  inch  in  diameter,  with  a 


62 


THE    MICROSCOPIST. 


pin  passing  through  it.     The  side  for  holding  the  object  is  to  be 
blackened;    the  other   side  is  covered  with  white   paper   on 


Fig.  21. 


which  the  name  is  written.  I  represents  another'plan,  for  very 
minute  objects;  the  pin  is  encased  with  blackened  wax  or 
cement,  or  passes  lengthwise  through  a  small  cork  cylinder. 

Fig.  22. 


Another  method  is  seen  at  e,  which  consists  of  a  small  cylinder 
of  cork  or  felt  with  a  pin  passing  transversely.  These  must 
be  blackened  with  common  lacquer  (shell-lac  dissolved  in  alco- 


MOUNTING    AND    PRESERVING    OBJECTS.  63 

hol)  and  lampblack,  holding  them  over  a  candle  to  dry. 
Sometimes  these  cylinders  are  made  of  ivory,  with  the  inside 
turned  hollow  like  a  small  box;  the  pin  runs  through  them  as 
at  c,  and  supports  the  object.  The  ivory  is  dyed  black  and 
the  inner  surface  made  as  sombre  as  possible.  Mr.  Quekett 
recommends  to  place  the  objects  on  pieces  of  cork  glued  to  the 
bottom,  side,  or  cover,  of  small  pill-boxes,  as  seen  in  Fig.  22. 
Opaque  objects  should  always  be  viewed  with  a  black  ground, 
and  the  darker  the  object,  the  more  sombre  must  be  the 
mounting.  White  is,  of  all  colours,  the  worst  which  can  be 
employed,  unless  the  object  is  totally  black. 


MOUNTING   CRYSTALS   FOR   POLARIZED   LIGHT. 

These  must  be  so  enclosed  that  the  air  is  completely  ex- 
cluded, otherwise  a  change  will  take  place,  and  the  objects  be 
spoiled.  When  it  can  conveniently  be  done,  it  is  well  to 
mount  them  in  Canada  balsam.  Sir  David  Brewster  recom- 
mends mixing  cold-drawn  castor  oil  with  the  Canada  balsam. 
In  this  case  the  edges  of  the  thin  glass  cover  should  be  ce- 
mented, as  the  castor  oil  prevents  the  balsam  from  becoming 
hard. 

Each  preparation  should  be  properly  labelled,  either  with  a 
writing  diamond  on  the  glass  slide,  or  on  the  paper  cover  of  the 
slide;  and  it  may  save  trouble  if  this  be  invariably  performed 
as  soon  as  mounted. 


CHAPTER  VI. 

ON    PROCURING   OBJECTS   FOR   THE    MICROSCOPE. 

•  THE  topic  suggested  by  the  title  of  this  chapter  is  almost 
endless;  for  the  microscopist  may  claim  contributions  from 
every  department  of  natural  science.  The  animal,  vegetable, 
and  mineral  kingdoms,  all  offer  him  interesting  objects  of  in- 
vestigation. We  shall  content  ourselves  with  noticing  some 
of  the  most  important  or  attractive  in  each  department. 

INORGANIC. 

Agate. — This  form  of  silica  is  often  found  imperfectly  crys- 
tallized, and  thin  plates,  prepared  by  the  lapidary's  wheel,  j^th 
of  an  inch  thick,  exhibit  a  rich  motley  colouring  when  viewed 
by  polarized  light. 

Carbonate  of  Lime. — Small  spherules  of  this  substance  are 
sometimes  found  in  the  urinary  deposits  of  the  horse.  They 
are  often  composed  of  concentric  layers;  at  other  times  the 
fibres  are  radial.  Illuminated  by  polarized  light  under  a  power 
of  100  diameters,  they  are  splendid  objects. 

Crystallization  of  Salts. — Independently  of  the  beautiful 
forms  assumed  by  different  salts  during  their  crystallization,  a 
great  variety  of  forms  may  be  obtained  by  mixing  small  quan- 
tities of  the  different  solutions  in  a  little  weak  gelatine,  starch, 
mucus,  &c.  To  procure  specimens,  put  a  drop  or  two  of  water, 


PROCURING    OBJECTS.  65 

solution  of  gelatine,  &c.,  upon  a  slide,  put  into  it  a  drop  of 
some  strong  solution  of  salts,  as  Epsom  salts,  hydrochlorate  of 
ammonia,  tartaric  acid,  &c.  Hold  the  slide  over  the  spirit- 
lamp  until  evaporation  is  perceived,  when  it  should  be  removed 
and  placed  under  the  microscope.  If  the  evaporation  is  too 
rapid,  the  crystals  will  not  be  well  formed.  They  may  be 
mounted  dry,  or  in  balsam.  A  power  of  30  diameters  is 
generally  sufficient.  Crystals  of  salts  form  interesting  and 
splendid  objects  under  polarized  light. 

Ice.  — A  plan  for  observing  the  crystallization  of  water  is  as 
follows.  Mix  some  water  with  a  little  charcoal,  chalk,  &c.,  in 
such  manner  that  a  number  of  fine  particles  may  be  mechani- 
cally suspended  in  it;  then  take  a  glass  slide,  place  it  on  a 
cold  night  in  an  exposed  situation,  as  outside  of  a  window-sill ; 
pour  upon  it  as  much  water  as  it  will  support  without  running 
over  the  edge,  and  let  it  remain  all  night.  The  next  morning, 
if  the  weather  has  been  sufficiently  cold,  and  the  atmosphere 
dry,  neither  water  nor  ice  will  be  seen  on  the  slide ;  but  the 
particles  of  charcoal  will  be  found  arranged  in  the  various 
forms  which  they  assumed  while  the  water  crystallized.  The 
slide  may  be  carefully  prepared  with  Canada  balsam  for  pre- 
servation. 

Crystals  of  Iron  Pyrites,  and  other  substances;  Oolites;  and 
various  sorts  of  sand;  are  interesting  objects.  The  sand  from 
Turkey  sponge,  and  from  the  sea,  often  contains  minute  shells 
of  various  kinds,  as  the  foraminifera,  &c.,  corallines,  and  other 
zoophytes. 

Sections  of  Granite,  Limestone,  &c.,  are  also  of  considerable 
interest;  but  sections  of  coal,  made  very  thin,  so  as  to  be  viewed 
by  transmitted  light,  develope  clearly  its  vegetable  origin,  and 
are  therefore  of  special  importance. 

Deut-Ioduret  of  Mercury. — The  change  of  colour  in  this  salt 
is  a  beautiful  object.  If  a  little  of  it  be  placed  in  a  watch- 


66  THE     MICROSCOPIST. 

glass,  having  another  inverted  over  it,  and  then  the  lower  one 
heated  over  the  flame  of  a  spirit-lamp,  the  salt  will  be  sub- 
limed. Placed  on  the  stage  of  the  microscope,  with  a  power 
of  30  diameters  adjusted  to  focus  at  the  inner  surface  of  the 
upper  glass,  minute  crystals  will  be  seen  to  form  of  a  bright 
yellow  colour,  which,  as  they  cool,  return  to  the  original  red. 


VEGETABLE   TISSUES. 

Vegetable  Tissues  are  prepared  by  tearing,  making  thin  sec- 
tions, maceration  in  water,  dissection,  or  are  examined  in  their 
natural  state. 

The  spiral,  dotted,  and  reticular  vessels  of  plants  require 
generally  to  be  dissected  out,  which  is  to  be  done  under  a 
shallow  magnifier.  A  single  lens  of  one  inch  focus  will  an- 
swer very  well  for  this  purpose.  Having  procured  a  piece  of 
asparagus,  or  the  petiole  of  the  garden  rhubarb,  &c.,  cut  out  a 
piece  about  an  inch  long ;  split  it  open  with  a  sharp  knife  or 
scalpel,  examine  it  under  the  magnifier,  and  separate  with  a 
needle-point  any  of  the  vessels  you  require  from  the  surround- 
ing cellular  tissue.  This  process  is  facilitated  by  dropping  a 
little  water  on  the  specimen.  To  prevent  it  moving,  the  speci- 
men may  be  fixed  with  beeswax  during  the  dissection.  Ves- 
sels, ducts,  and  cellular  tissue,  when  prepared,  should  be  kept 
in  spirits  of  wine  until  mounted. 

Cuticles. — The  external  covering  of  plants,  or  cuticle,  con- 
sists of  a  thin  membrane,  adherent  to  the  cellular  tissue  be- 
neath it.  Under  the  microscope  it  appears  traversed  by  lines 
in  various  directions,  giving  its  surface  a  reticulated  appear- 
ance. The  form  of  these  reticulations  varies  in  different 
plants:  in  some  they  are  hexagonal,  in  others  prismatic  or 


PROCURING    OBJECTS.  67 

irregular.  Cuticles  may  be  mounted  dry  or  in  fluid.  The 
geranium,  oleander,  &c.,  afford  good  specimens. 

The  cuticle  of  the  under  side  of  the  leaf  of  many  plants, 
exhibits  under  the  microscope  dark  spots  among  their  reticu- 
lations. These  are  called  stoinata,  and  are  the  orifices  by 
which  a  function  analogous  to  respiration  in  animals  is  effected. 
They  also  serve  for  the  exit  of  water  from  the  plant  by  means 
of  evaporation.  Plants  destitute  of  stomata,  as  the  South 
American  Cacti,  &c.,  will  remain  in  a  hot  and  dry  atmosphere 
without  losing  their  moisture.  The  form,  number,  and  ar- 
rangement of  the  stomata  vary  in  different  plants. 

Cellular  Tissue  is  the  first  and  most  generally  developed 
simple  form  of  vegetable  life.  Its  primary  development  may 
be  seen  by  examining  a  small  portion  of  yeast  at  intervals 
under  the  microscope.  No  plant  is  without  cellular  tissue, 
and  many  are  destitute  of  any  other  kind  of  tissue,  as  the 
lichens,  and  some  fresh-water  algae.  A  section  of  the  pith  of 
elder,  pulp  of  peach,  &c.,  will  afford  specimens. 

The  petals  of  flowers  are  mostly  composed  of  cellular  tis- 
sue ;  their  brilliant  colours  arise  from  the  fluid  contained  with- 
in the  cellules.  These  form  excellent  microscopic  objects,  and 
when  mounted  in  balsam  are  permanent.  The  pelargoniums 
and  geraniums  are  among  the  most  interesting. 

The  petal  of  the  anagallis,  or  scarlet  chickweed,  is  a  beauti- 
ful object.  The  spiral  vessels  diverging  from  the  base,  and 
the  singular  little  cellules  which  fringe  the  edge,  are  worthy 
of  notice. 

Vascular  Tissue,  prepared  by  maceration  and  dissection, 
presents  many  interesting  subjects.  Spiral  vessels  consist  of 
membranous  tubes  with  conical  extremities,  internally  fur- 
nished with  one  or  more  spiral  fibres.  As  the  vessels  grow, 
the  spiral  fibre  breaks  into  short  pieces,  forming  rings.  The 
vessels  are  then  called  annular.  If  the  pieces  of  fibre  are  still 


68  THEMICROSCOPIST. 

shorter  they  are  called  dotted  or  reticulated  vessels.  The  root 
of  the  garden  rhubarb,  the  stem  of  the  hyacinth,  the  leek,  &c., 
furnish  examples. 

A  peculiar  form  of  vessel  is  met  with  in  the  common  car- 
rot ;  it  is  obtained  from  the  root  in  a  layer  between  the  yellow 
central  portion  and  the  red  annulus. 

Sections  of  Wood. — These  are  cut  thin,  so  as  to  allow  them 
to  be  viewed  as  transparent  objects.  Hard  woods,  containing 
gum,  resin,  &c.,  should  be  soaked  in  essential  oil,  alcohol, 
ether,  &c.,  before  mounting.  By  transverse  slices,  a  variety 
of  beautiful  lace-like  objects  may  be  obtained,  but  little  infor- 
mation is  acquired  from  them  of  the  real  structure  of  the  wood. 
For  this  purpose,  if  the  tree  is  of  the  endogenous  and  branch- 
less kind — which  grow  by  additions  to  the  interior — a  vertical 
section  is  also  necessary.  If  the  tree  be  an  exogen,  two  verti- 
cal sections  will  be  required  in  addition  to  a  transverse  one. 
The  exogens  grow  by  annual  layers  exteriorly  under  the  bark, 
and  are  branched.  In  these  one  of  the  vertical  sections  should 
be  radial  and  the  other  tangental.  The  radial  vertical  section 
will  show  the  number  and  size  of  the  medullary  rays ;  that  is, 
the  small  portions  of  pith  which  proceed  horizontally  from  the 
centre,  enclosed  in  a  sheath  of  woody  fibres.  The  frequency 
and  size  of  the  medullary  rays  determine  the  number  and 
strength  of  the  branches  of  the  tree.  This  section  also  ex- 
hibits in  coniferous  trees  (as  the  pine,  &c.),  the  beautiful  disc- 
like  glands  which  adhere  to  the  woody  fibres.  These  are 
beautiful  objects,  and  sometimes  require  a  power  of  200  or  300 
diameters.  The  tangental  vertical  section  is  a  slice  across  the 
medullary  rays;  it  exhibits  the  form  and  arrangement  of  the 
cellular  tissue  within  them.  All  the  vertical  sections  show  the 
form,  size,  and  connexion  of  the  woody  fibres ;  spiral,  reticu- 
lated, and  dotted  vessels,  &c. ;  and  are  far  more  instructive  than 
the  transverse  sections. 


PROCURING    OBJECTS.  69 

Charcoal. — Thin  sections  of  charred  wood  are  very  interest- 
ing and  instructive. 

Fossil  Woods. — Thin  sections  must  be  made  by  grinding  on 
a  lapidary's  wheel.  They  should  be  polished. 

Siliceous  Cuticles,  &c.,  from  equisetum,  straw,  cane,  &c., 
are  prepared  by  heat  in  a  covered  crucible,  or  by  boiling  and 
digestion  in  nitric  acid.  The  most  favourable  example  for 
showing  the  form  in  which  silica  occurs  in  plants,  is  the  husk 
of  the  oat  or  wheat.  If  a  husk  of  oat  be  examined  under  the 
microscope,  having  been  mounted  in  water  or  Canada  balsam, 
a  series  of  bright  parallel  columns,  serrated  on  each  side,  may 
be  observed  among  the  cellular  tissue  :  if  another  specimen  be 
burned  carefully  between  the  glasses,  and  the  ashes  be  mount- 
ed in  balsam,  the  siliceous  columns  will  still  be  seen.  In  the 
ashes  of  the  husk  of  wheat,  rows  of  concave  discs  may  be 
observed,  which  are  composed  of  some  metallic  oxide.  In  the 
ashes  of  the  calyx  and  pollen  of  the  mallow,  organized  lime 
may  be  detected.  In  the  ashes  of  coal,  a  variety  of  vegetable 
structures,  as  cellular  tissue,  spiral  vessels,  &c.,  may  be  dis- 
covered. In  these  experiments  it  is  necessary  to  render  the 
ashes  transparent  by  immersion  in  balsam. 

Hairs,  Down,  &c.,  from  leaves  and  stems,  are  generally 
opaque  objects.  In  the  plants  which  produce  cotton,  the  hairs 
are  attached  to  and  envelope  the  seeds.  Hairs  are  composed 
of  cellular  tissue.  Their  functions  are  said  to  be  either  lym- 
phatic or  secreting.  They  offer  great  varieties  in  form,  some 
being  stellated,  others  forked  or  branching. 

Pollen  may  be  mounted  in  Canada  balsam;  or,  if  rather 
transparent,  in  fluid ;  or  dry.  Sometimes  the  grains  are  inte- 
resting opaque  objects.  The  common  form  of  the  pollen  or 
farina  of  flowers  is  spherical,  with  a  smooth,  punctured,  or 
spiny  surface ;  but  some  are  square,  others  cylindrical,  oval  with 
attenuated  extremities,  or  triangular  with  convex  sides.  The 
pollen  of  the  passion  flower  is  very  curious,  and  if  immersed 


70  THE    MICROSCOPIST. 

in  very  diluted  sulphuric  acid  opens  and  disperses  the  grains. 
The  pollen  of  Datura  stramonium,  or  Jamestown  weed,  and 
others,  when  immersed  in  a  few  drops  of  weak  acid  placed 
upon  a  slide  under  the  microscope,  emits  a  tube  of  some 
length.  The  granular  matter  in  the  pollen  may  then  be  seen 
to  pass  along  the  tube  until  the  pollen  is  emptied.  The  diameter 
of  the  pollen  varies  considerably  in  different  plants ;  among  the 
smallest  are  those  of  the  Sensitive  Plant. 

/Starch. — The  granules  of  starch  (not  the  ordinary  impure 
starch  of  the  laundress)  obtained  from  different  plants,  are 
found,  when  examined  under  the  microscope,  to  differ  in  size 
and  form.  Some  are  spherical,  others  elliptical,  flask-shaped, 
polyhedral,  &c.  Hence  this  method  of  examination  affords 
a  ready  means  of  detecting  fraud  in  the  substitution  of  one 
kind  of  grain  for  another.  Starch  granules,  although  so  very 
minute,  are  composed  of  a  fine  and  delicate  membrane,  enclos- 
ing a  fine  mealy  powder.  It  may  be  compared  in  some  re- 
spects to  a  common  pea,  in  which  the  legumen  is  enclosed  in 
a  testa  or  skin.  Starch  granules  are  not  soluble  in  cold  water, 
nor  is  iodine  capable  of  acting  on  them  while  the  membrane 
enclosing  its  contents  remains  whole.  If  the  granules  be  tritu- 
rated or  immersed  in  hot  water,  the  membrane  will  be  ruptured, 
and  iodine  will  then  turn  them  blue.  Starch  is  readily  sepa- 
rated from  wheat,  potato,  arrow-root,  &c.,  by  repeated  washings 
in  cold  water.  To  obtain  it  from  rice,  the  grains  should  be 
macerated  for  a  few  days,  and  to  prevent  the  decomposition  of 
the  gluten,  a  little  soda  should  be  added  to  the  macerating 
water.  Under  the  microscope,  the  surface  of  starch-grains 
often  appears  corrugated,  and  each  of  them  has  one  or  two 
bright  spots,  called  the  hilum,  which  is  supposed  to  be  the 
part  where  the  starch  adheres  to  the  cell.  Under  polarized 
light  they  present  the  beautiful  phenomenon  of  the  black 
cross.  They  should  be  mounted  dry,  and  protected  from  the 
pressure  of  the  upper  glass  by  a  rim  of  thin  paper. 


PROCURING    OBJECTS.  71 

Seeds  are  generally  opaque  objects,  and  present  a  great 
variety  of  beautiful  and  interesting  forms. 

Hard  Tissues,  the  stones  and  shells  of  nuts,  &c.,  are  pre- 
pared like  bone,  &c.,  by  cutting  and  grinding.  Some  require 
the  lapidary's  wheel. 

Raphides,  or  crystals  from  the  interior  of  plants.  If  the 
leaf  or  bulb  of  a  common  hyacinth  be  wounded,  a  discharge  of 
fluid  ensues ;  if  this  be  received  on  a  slide  and  submitted  to 
the  microscope,  a  number  of  minute  acicular  bodies  will  be 
observed  floating  in  the  liquid.  They  are  called  raphides. 
They  are  common  in  many  plants.  By  scraping  hickory,  or 
other  bark,  on  to  a  slide,  moistening  it  with  the  breath,  and 
blowing  off  the  woody  particles;  or  by  placing  a  part  of  the 
ashes  of  a  burnt  maple  leaf,  coat  of  an  onion,  &c.,  on  a  slide, 
such  crystals  may  be  seen.  They  may  be  mounted  dry  or  in 
balsam. 

Mosses,  are  supposed  to  be  destitute  of  woody  fibre  and  vas- 
cular tissue.  When  a  leaf  is  carefully  examined,  the  septa 
which  divide  the  cells  are  sometimes  found  to  take  a  spiral 
course.  To  observe  this  structure,  soak  the  moss  in  water,  to 
expand  the  cells. 

It  is  essential,  in  collecting  mosses,  to  preserve  the  theca  or 
seed-vessel,  for  without  it  the  genera  cannot  be  determined ; 
while  this  part,  with  the  calyptra  and  operculum,  arc  the  most 
valuable  for  the  microscope. 

Algae.. — Are  interesting  objects.  The  green,  mucous,  slime- 
like  matter  in  damp  garden  walks,  and  the  hair-like  weeds  in 
ditches,  are  examples  of  fresh-water  algse.  The  sea-weeds  of 
our  coast  are  marine  algse,  and  are  often  found  having  zoo- 
phytes adhering  to  them ;  they  are  then  splendid  opaque  ob- 
jects. For  mounting  in  balsam,  the  smaller  kinds,  of  a  bright 
scarlet  colour,  are  the  most  valuable. 

Ferns. — The  genera  are  mainly  distinguished  by  the  posi- 
tion and  arrangement  of  the  organs  of  reproduction.  These 


72  THE    MICROSCOPIST. 

are  mostly  on  the  under  side,  or  along  the  margin  of  the  leaf 
or  frond.  They  are  best  examined  as  opaque  objects.  They 
should  be  collected  before  they  are  quite  ripe.  The  spores 
(seeds)  are  usually  enclosed  in  brown  capsules,  each  having 
an  elastic  ring  about  its  equator,  which  when  ripe  bursts,  and 
the  spores  are  dispersed  to  a  distance.  Spores  may  be  mounted 
either  as  transparent  or  opaque  objects.  The  development  of 
ferns  may  be  observed  by  placing  the  spores  in  moistened 
flannel  and  keeping  it  at  a  warm  temperature.  At  first  a  single 
cellule  is  produced,  then  a  second,  and  so  on.  After  this  the 
first  cellule  divides  into  two,  and  then  the  others,  by  which  a 
lateral  increase  takes  place. 

Lichens  and  Fungi  afford  interesting  objects.  The  various 
kinds  of  mildew  upon  vegetable  substances  are  familiar  ex- 
amples of  minute  fungi. 

Organic  Fabrics  possess  much  interest  in  a  commercial 
point  of  view,  in  addition  to  the  curiosity  arising  from  the 
manner  in  which  the  threads  or  bundles  of  fibres  are  woven  or 
interlaced.  For  this  purpose  they  should  be  examined  as 
opaque  objects  on  a  black  ground,  with  a  magnifying  power 
of  from  30  to  60  diameters.  The  fibres  of  cotton  are  readily 
distinguished  under  the  microscope  from  those  of  linen,  wool, 
&c.  Cotton  fibres  are  tubular,  and  are  formed  of  pure  cellular 
tissue.  These  tubes,  from  the  thinness  of  their  sides,  often 
collapse  and  appear  like  flat  ribbons  or  bands.  The  reason 
assigned  for  the  preference  given  to  linen  (flax)  over  cotton 
for  lint,  for  surgical  purposes,  is  that  the  fibres  of  the  former 
are  solid  cylinders  of  woody  fibre,  while  the  edges  of  the 
flattened  bands  of  the  latter  are  supposed  to  irritate  the 
wounds. 

Circulation  in  Vegetables. — The  circulation  in  plants,  termed 
cyclosis,  is  a  revolution  of  the  fluid  contained  in  each  cellule, 
and  is  distinct  from  those  surrounding  it.  It  can  be  observed 
in  all  plants  in  which  the  circulating  fluid  contains  particles  of 


PROCURING    OBJECTS.  73 

a  different  refractive  power  or  intensity,  and  the  cellules  are  of 
sufficient  size  and  transparency.  Hence  all  lactescent  plants, 
or  those  having  a  milky  juice,  with  the  other  conditions,  ex- 
hibit this  phenomenon.  The  following  aquatic  plants  are 
generally  transparent  enough  to  show  the  circulation  in  every 
part  of  them  :  —  Nitella  hi/alina,  Nitella  translucens.  Char  a 
vulgarisj  and  Caulinia  frag  ills.  In  the  Frogbit  (Hydrocharis), 
it  is  best  seen  in  the  scales  surrounding  the  leaf-buds,  with  a 
power  between  60  and  200  diameters. 

The  jointed  hairs  of  the  filament  of  the  anther  in  Trandes- 
cantia  mrginica  (Spiderwort) ;  the  delicate  hairs  on  the  leaf- 
stalk of  Senecio  vulgaris  (Groundsel) ;  and  a  section  of  the 
leaf  of  Vallisneria  spiralis,  will  show  the  circulation,  especially 
when  viewed  with  a  high  power. 


ANIMAL    TISSUES,    ETC. 

INFUSORIA. — These  minute  animals,  some  of  which  are 
only  the  2  j^^th  part  of  an  inch  in  diameter,  are  extremely 
numerous.  Between  700  and  800  different  species  have 
been  discovered  and  described.  Dr.  Ehrenberg,  to  whom  we 
are  indebted  for  much  of  our  knowledge  respecting  the  ani- 
malculse,  divides  them  into  two  classes,  i.  e.,  Polygastrica  and 
Rotatoria.  The  first  class  is  so  named  from  their  possessing  a 
digestive  apparatus  composed  of  many  globular  vesicles,  which 
perform  the  functions  of  stomachs.  The  Rotatoria  are  so 
called  from  their  possessing  rotary  organs  about  their  mouth. 
These  are  much  more  highly  organized  than  the  others.  The 
Polygastrica  increase  by  self-division,  or  by  the  growth  of 
gemmules  or  buds  upon  their  bodies ;  the  Rotatoria  are  herma- 
phrodite, and  oviparous.  Many  animalculae  are  loricated ;  or 
protected  by  a  shell,  or  shield,  which  is  generally  siliceous  : 
others  are  destitute  of  such  an  appendage. 

7 


74 


THE     MICROSCOPIST. 


The  following  table  exhibits  the  families  or  groups  into 
which  this  interesting  department  of  animal  life  has  been  divi- 
ded by  Ehrenberg.  Those  who  wish  further  information  re- 
specting them  are  referred  to  his  work  "Die  Infusionsthier- 
chen/'  or  to  Pritchard's  "  History  of  Infusoria,  Living  and 
Fossil."  Dr.  Mantell' s  work  on  Animalcules  contains  also 
much  valuable  information. 


CLASS   I.     POLYGASTRICA. 


J 

,.S®1?"       (illoricated  or  shell-less, 

Monadina. 

§C3 

cl7le0teJloricatedorshelled' 

Cryptomonadina. 

Body 

1 

destitute  of 
appendages. 

Form 
of  body  ' 

self-divi- 
sion in- 

self-dividing on  all         1 
sides  (globular),          J 

Volvocina. 

§ 

(No  foot-like  < 
processes.) 
Gymnica. 

constant. 

complete,  < 
hence 
formed  in 

self-dividing  1  il]oricated 

"miCtM'o"^'' 

Vibriona. 
Closterina. 

o 

clusters. 

4* 

Form 
of  body 

illoricated, 



Astasiaea. 

| 

variable. 

loricated, 

Dinobryina* 

{illor 

icated, 

..... 

Amoebaea. 

5 

loric 

f  compound    foot-like  process"! 
ated  J    fr°m  one  aperture,                 j 

Arcellina. 

1 

'  '  )  simple  foot-like  process  from  ) 
[   one  or  from  each  aperture,    j 

Bacillaria. 

i 

Hairy             UHoricated,     

Cyclinida. 

•nj             Epitricha.         \  loricated,    

Peridinaea. 

One  receiving  atad  f 

Vrtvf  i  f*&\  1  ?  -n  Q 

d 

0 

uiscnarging  orince  »  11101 
only  for  nutrition.  |  lori( 

o+£lrl 

v  orticeinna. 
Ophrydina. 

8 

Anopisthia.         \_ 

Two  ditto  orifices,  ( 

a 

one  at  each        j  illoi 

icated,     - 

. 

Enchelia. 

§ 

ovf  rnmit-xr                  '    Irvvi 

%  A  4-  A/1 

§ 

Enantritena.        (_ 

Colepina. 

is 

T 

A  .fiooa    .,  ,otnrl    f                   (mouth  furnished  with  pro-  \ 
obliaue           J  illoricated,  <  boscis,  tail  absent,                j 

Trachelina. 

f 

Allotreta.         } 

(  mouth  anterior,  tail  present, 

«n4-A^ 

Ophryocercina. 

1 

Orifices  abdomi-    f  inoric  ted  \  l°com°tive  organs  cilii, 
nal.                                '  (       do.  ,        do.      various, 

Kolpodea. 
Oxytrichina. 

"Rnrvlnt,a. 

PROCURING    OBJECTS.  75 


CLASS   II.     ROTATORIA. 


With  a  simple  con-     «"*"  *  <™™        -tire.        moricated,  Icthydm, 


tmuous^eath   of        argin    of 

(Jfonofo-ocfta.)        [  wSSJSa.  )loricated,    Floscularia. 

(with  the  cilii-wreath  divided  into  J  illoricated,  Hydatinea. 
several  series.  )  loricated,    Euchlanidota. 

Polytrocha. 


In  reference  to  obtaining  infusoria,  some  persons  imagine 
that  if  they  procure  a  portion  of  fetid  ditch-water,  or  take 
a  few  flowers,  &c.,  and  macerate  them  in  water,  they  will  be 
furnished  in  a  few  days  with  all  the  varieties  they  may  desire  ; 
but  this  is  not  the  case.  Infusoria  will  of  course  be  found, 
but  they  will  be  only  of  the  most  ordinary  kinds.  To  obtain 
those  of  higher  interest,  some  degree  of  skill  is  required. 
Many  remarkable  species  have  been  taken  in  meadow-trenches 
in  the  slowly  running  water,  after  a  summer  shower,  especially 
about  the  time  that  the  first  crop  of  hay  was  mown.  Among 
healthy  water-plants,  the  various  kinds  of  Vorticellina  (Sten- 
tors  and  Vorticetlse,  or  trumpet  and  bell-shaped  infusoria),  and 
Rotatoria  (wheel-animalcules),  may  be  sought  for  with  success. 
The  stems  of  aquatic  plants  have  often  the  appearance,  to  the 
naked  eye,  of  being  encased  with  mouldiness,  or  mucor,  which 
on  being  examined  with  the  microscope,  proves  to  be  an  ex- 
tensive colony  of  arborescent  animalcules.  The  dust-like 
stratum  sometimes  seen  on  the  surface  of  ponds,  and  the 
shining  film  which  sometimes  covers  water-plants,  assuming 
various  hues  of  red,  brown,  yellow,  green,  and  blue,  is  caused 
by  the  presence  of  infusoria,  some  of  which  are  very  beautiful. 
Many  species  live  in  the  clean  fresh  water  of  rivers,  lakes,  and 
springs  ;  and  the  brine  of  the  ocean,  likewise,  as  well  as  the 


76  THE    MICROSCOPIST. 

mould  on  the  surface  of  the  earth,  has  its  microscopic  inhabi- 
tants. 

In  order  to  procure  animalculae,  provide  yourself  with  a 
number  of  clean,  wide-mouthed,  glass  phials,  fitted  with  proper 
corks,  not  glass  stoppers,  so  that  the  air  may  have  access  to 
them,  at  least  to  some  extent.  Have  also  a  rod,  or  walking- 
cane,  which  may  be  prepared  with  a  spring-hook  and  ferule  for 
fastening  a  phial  on  its  end,  although  a  piece  of  twine  is  a 
good  substitute.  On  reaching  the  pond,  &c.,  carry  the  phial 
(attached  to  the  rod)  in  an  inverted  position,  and  when  at 
proper  depth,  or  in  the  neighbourhood  of  water-plants,  it  should 
be  turned  quickly,  when  animalculae,  &c.,  will  run  into  it. 
Water-fleas  and  Daphnia3  should  be  frightened  away  by  shak- 
ing the  phial  before  turning.  If  in  the  phial,  they  go  quickly 
to  the  bottom,  and  the  upper  water  can  be  poured  off.  Exa- 
mine the  water  with  a  pocket  lens,  and  preserve  the  animal- 
culae. 

The  indications  of  the  presence  of  infusoria  are  specks  mov- 
ing about  in  the  water,  or  an  apparent  mouldiness  around  the 
stalks  of  the  water-plants,  &c.,  which  may  have  been  caught 
in  the  phial.  If  these  appearances  be  not  discerned  by  the 
magnifier,  the  water  may  be  thrown  away,  and  another  place 
resorted  to.  A  small  portion  only  of  vegetable  matter  should 
be  preserved  in  the  phial,  as  its  decay  may  soon  kill  the  ani- 
malcules. 

Small  newts  and  many  larvae  should  be  preserved ;  the  for- 
mer especially,  as  they  eat  up  the  Daphniae,  Monoculi,  &c., 
that  destroy  the  Yorticellae.  In  the  branchiae  of  young  newts, 
too,  and  in  their  feet,  the  circulation  of  the  blood  is  beautifully 
seen. 

The  phial  should  sometimes  be  laid  horizontally  on  the  bot- 
tom of  the  pond,  and  scrape  the ,  surface  of  the  mud.  This 
should  be  put  in  a  large  jar  with  water,  and  in  a  day  or  two 


PROCURING    OBJECTS.  77 

the  animalculse  will  be  on  the  surface  of  the  mud,  from  which 
they  can  be  removed  with  the  fishing-tubes  (see  page  47),  and 
placed  under  the  microscope. 

If  the  creatures  are  too  minute  to  be  seen  easily  with  the 
naked  eye,  pour  a  little  water  from  the  vessel  containing  them 
into  a  watch-glass,  and  place  it  on  a  piece  of  card-board,  ren- 
dered half  black  and  half  white.  The  white  ground  will  make 
the  dark  specimens  apparent,  and  vice  versa.  They  can  then 
be  seen  with  the  pocket  lens,  and  taken  out  with  the  fishing- 
tubes. 

In  order  to  show  the  stomachs,  cilia,  &c.,  of  animalculae 
under  the  microscope,  rub  some  pure  sap-green  or  carmine  on 
a  palette  or  plate  of  glass,  and  add  a  few  drops  of  water.  If 
the  glass  be  now  held  on  one  side,  a  portion  of  the  colouring 
matter  may  be  put  into  the  water  on  the  slide  containing  the 
animalcule.  If  they  be  vorticellse  or  rotiferas,  the  particles  of 
colouring  matter  will  show  the  vibratile  actions  of  the  cilia, 
whilst  other  particles,  swallowed  by  the  animals,  will  give  a 
rich  tint  to  the  compartments  of  their  alimentary  canal. 

Fossil  Infusoria. — A  great  number  of  infusorial  earths  may 
be  mounted  in  balsam  (test  objects  dry,  however,)  without 
washing,  &c.,  but  others  must  be  repeatedly  washed  or  digested 
in  acid.  For  the  skeletons  or  shields  in  carbonate  of  lime,  Pro- 
fessor Ehrenberg  has  directed  to  place  a  drop  of  water  on  the 
slide,  and  put  into  it  as  much  scraped  chalk  as  will  cover  the 
fine  point  of  a  knife,  spreading  it  out,  and  leaving  it  to  rest  a 
few  seconds;  then  withdraw  the  finest  particles,  which  are 
suspended  in  the  water,  together  with  most  of  the  water,  and 
let  the  remainder  become  perfectly  dry.  Cover  this  with 
Canada  balsam,  and  hold  it  over  a  lamp  until  it  becomes  slight- 
ly fluid,  without  froth. 

Siliceous  Shields  of  Infusoria,  such  as  those  in  guano, 
Richmond  earth,  &c.,  require  to  be  well  washed,  and  boiled  or 


78  THE     MICROSCOPIST. 

digested  in  nitric  or  hydrochloric  acid.  After  this,  a  small 
quantity  of  the  sediment  in  which  they  are  contained  should 
be  placed  on  a  number  of  slides,  and  those  containing  the  best 
specimens  laid  aside  for  mounting. 

Sponges. — These  lowly-organized  bodies  are  found  both  in 
salt  and  fresh  water  in  all  parts  of  the  globe.  Many  of  them 
are  very  minute,  and  may  be  examined  without  much  prepa- 
ration, but  others  require  to  be  burned,  or  acted  on  by  acid, 
to  show  the  small  masses  of  flint,  called  spicula,  which  form 
their  rudimentary  skeleton,  as  well  as  other  masses  of  the 
same  material,  which  enter  largely  into  the  framework  of  the 
young  sponges  or  gemmules. 

Corals  are  best  examined  by  horizontal  and  vertical  sec- 
tions. If  the  animal  matter  only  is  required,  the  sections  may 
be  macerated  in  hydrochloric  acid,  to  which  five  or  six  times 
its  bulk  of  water  has  been  added. 

Zoophytes. — Residents  at  the  sea-side,  or  occasional  visitors, 
when  provided  with  a  microscope,  have  frequent  opportunities 
of  examining  some  of  these  most  elegant  of  animal  forms. 
Scarcely  a  piece  of  sea-weed  or  fragment  of  shell  will  be 
found,  that  does  not  afford  a  habitation  for  some  member 
of  this  interesting  family.  The  animals  are  generally  found 
in  clusters,  or  compound,  sometimes  communicating  at  a  com- 
mon centre;  at  other  times  distinct  and  only  connected  by 
the  solid  matter  of  which  their  polypidoms  are  formed.  Some 
few,  as  the  common  fresh-water  polype,  do  not  secrete  any 
hard  substance  either  around  or  within  them. 

INSECTS. — These  afford  the  most  numerous  and  beautiful 
objects  for  examination,  as  there  is  scarcely  a  part  of  the  body 
of  an  insect  that  does  not  exhibit  some  remarkable  structure. 

Antennse. — The  horns  of  insects  not  only  vary  in  form  in 
different,  genera,  but  in  the  male  and  female  of  the  same 
species.  They  may  be  mounted  as  opaque,  or  in  Canada 
balsam. 


PROCURING    OBJECTS.  79 

Eggs. — The  eggs  of  insects  are  generally  of  an  oval  form, 
the  outer  covering  being  sufficiently  rigid  to  resist  ordinary 
external  impressions;  others  are,  however,  soft  and  pliant.  In 
some  species  they  are  globose,  as  in  many  Lepidoptera;  or 
conical,  as  in  the  large  white  cabbage-butterfly;  cylindrical, 
pear-shaped,  barrel-shaped,  &c.  They  are  for  the  most  part 
smooth ;  but  many  are  very  beautiful,  ornamented  with  symme- 
trical ridges,  canals,  dots,  &c.,  giving  them,  as  Reaumer  ob- 
served, the  appearance  of  embossed  buttons.  Some  are  fur- 
nished with  appendages  for  peculiar  purposes.  Thus  the  eggs 
of  the  dung-fly  (Scatophaga  putris)  has  two  oblique  props  at 
one  end,  to  prevent  it  sinking  too  deep  in  the  matter  upon 
which  it  is  deposited,  while  those  of  the  water-scorpion  (^Nepa 
cinered)  are  furnished  with  a  coronet  of  spines,  forming  a  re- 
ceptacle for  the  egg  which  is  deposited  immediately  after- 
wards. Sometimes,  one  end  of  the  egg  is  provided  with  a 
sort  of  cap  or  lid ;  at  other  times  the  egg  is  in  one  piece,  and 
the  enclosed  larva  must  gnaw  or  burst  through  it.  The  colour 
is  very  various,  although  white,  yellow,  and  green  are  the 
most  prevalent  tints. 

In  many  species  the  eggs  are  deposited  singly;  in  others, 
they  are  discharged  en  masse.  Some  arrange  them  symme- 
trically, and  others  enclose  them  in  a  mass  of  gluten,  espe- 
cially those  whose  larvae  inhabit  the  water.  Many  species  em- 
ploy a  gummy  matter  to  attach  them  firmly  to  the  substances 
on  which  they  are  placed ;  while  some,  as  the  yellow-tail  moth 
(Arctia  chrysorrhcea),  wrap  them  in  a  coating  of  down,  which 
they  pull  off  their  own  bodies ;  and  the  lackey  moth  (Lasio- 
campa  Neustria),  deposits  her  eggs  in  a  spiral  coil  round  the 
stems  of  fruit  trees. 

Most  varieties  require  to  be  viewed  as  opaque  objects  under 
a  power  of  30  to  60  diameters. 

Elytra,  or  wing-cases  of  insects,  are  often  singularly  en- 
graved and  coloured,  and  form  the  most  brilliant  of  all  opaque 


80  THE     MICROSOOPIST. 

objects.  Some  are  covered  with  beautiful  iridescent  scales, 
and  others  are  furnished  with  branched  hairs.  Some  of  them 
are  much  improved  by  being  mounted  in  a  thick  cell  with 
Canada  balsam,  while  others  lose  much  of  their  splendour  by 
being  so  treated.  In  order  to  ascertain  whether  an  elytron 
will  be  improved  by  the  balsam,  one  of  the  legs,  or  some  part 
supplied  with  a  few  of  the  iridescent  scales,  should  be  touched 
with  turpentine;  if  the  brilliancy  be  increased,  it  may  be 
mounted  in  balsam,  if  otherwise,  dry.  The  elytra  of  some 
beetles,  after  having  been  softened  in  caustic  potash,  may  be 
mounted  between  flat  glasses,  as  ordinary  objects. 

Eyes  of  Insects,  Arachnida,  &c. — The  structure,  number, 
and  form  of  the  eyes  of  insects  may  be  ranked  among  the 
most  curious  parts  of  natural  history.  They  are  generally 
hemispherical,  on  each  side  of  the  head,  but  sometimes  they 
are  oval  or  kidney-shaped.  When  closely  examined,  they  are 
found  to  consist  of  a  vast  number  of  minute  lenses,  generally 
hexagonal,  but  sometimes  quadrangular  or  circular.  In  the 
ant  there  are  50  of  such  lenses  in  each  eye;  in  the  common 
house-fly  4000;  in  the  dragon-fly  12,500;  and,  according  to 
G-eoffroy,  in  the  eye  of  a  butterfly  34,650.  When  one  of  the 
eyes  is  detached  from  the  head  and  cleaned,  the  lenses  are 
found  to  be  as  clear  as  crystal.  If  a  cluster  of  eyes  be  placed 
under  the  microscope,  at  a  distance  without  its  focus  equal  to 
their  focal  length,  the  lens  of  each  eye  will  exhibit  a  distinct 
image  of  a  candle,  &c.,  placed  before  it. 

The  external  form  of  the  eye  may  be  seen  in  situ  in  all  in- 
sects when  viewed  as  opaque  objects,  but  the  layer  of  lenses 
requires  the  aid  of  maceration  and  dissection  to  free  them 
from  a  considerable  amount  of  pigment.  They  may  then  be 
mounted  dry,  in  fluid,  or  in  balsam.  If  required  to  be  flat, 
they  must  be  made  so  by  pressure  while  soft,  otherwise  they 
are  liable  to  split. 


PROCURING    OBJECTS.  81 

If  the  eye  of  a  fly,  or  other  insect,  properly  prepared  by 
mounting  in  balsam,  be  held  near  the  eye  of  an  observer  who 
looks  through  it  at  a  distant  candle,  &c.,  the  interference  of 
light  in  the  minute  lenses  will  cause  a  number  of  images  to  be 
perceived,  tinged  with  beautiful  colours. 

The  eyes  of  spiders  are  single.  They  have  from  four  to 
twelve,  variously  arranged.  Some  insects  have  also  single 
eyes  in  addition  to  the  compound  eyes  before  noticed. 

Feet. — The  structure  of  the  feet  of  those  insects  which  sup- 
port themselves  on  polished  surfaces,  and  against  the  force  01 
gravity,  is  very  remarkable,  and  it  is  doubtful  if  it  be  yet  per- 
fectly understood.  Some  suppose  them  to  act  as  suction-pads, 
others  that  they  secrete  a  viscid  fluid  by  means  of  which  they 
stick  with  sufficient  force  to  enable  them  to  walk.  The  latter 
theory  is  rendered  most  probable  by  microscopic  researches. 

The  number  of  pads  on  each  foot  is  variable. 

The  anterior  and  middle  pairs  of  feet  of  the  male  Dytiscus 
are  furnished  with  curious  disc  or  cup-shaped  appendages  on 
the  inside  of  the  leg.  They  may  be  viewed  as  opaque  and  in 
balsam. 

Hairs  of  Insects,  &c.,  may  be  mounted  dry,  in  fluid,  or  in 
balsam.  In  some  spiders  the  hairs  are  branched;  in  the  larvae 
of  many  insects  they  are  covered  with  spines,  as  the  hairs  of 
caterpillars,  &c. ;  and  in  the  Crustacea  they  are  provided  with 
spines,  or  plumed  like  a  feather.  The  hairs  and  scales  of  in- 
sects will  be  further  treated  of  in  the  chapter  on  Test  Objects. 

Heads,  Mouths,  &c. — The  manducatory  apparatus  of  insects 
is  a  subject  of  great  interest  to  the  entomologist.  The  divi- 
sion of  insects  into  Mandibulata  and  Haustellata  are  founded 
thereon ;  the  first  having  jaws,  the  latter  a  proboscis  or  suck- 
ing instrument.  Some  of  them  require  but  little  preparation, 
and  may  be  mounted  as  opaque  objects;  others,  as  the  pro- 
bosces  and  lancets  of  flies  and  bees,  demand  considerable  skill 


82  THEMICROSCOPIST. 

to  display  them  to  the  best  advantage.  When  thin  and  trans- 
parent, they  should  be  mounted  in  fluid,  but  if  thick  and  opaque, 
in  balsam.  Before  mounting  in  the  latter  way,  they  should  be 
dissected  while  soft,  and  laid  out  on  a  slide  to  dry. 

Parasitic  Insects  should  be  placed  in  spirit  and  water  in 
order  to  kill  them.  They  may  be  mounted  in  fluid  or  balsam. 
Some  of  the  large  kinds  may  be  examined  as  opaque  objects. 
The  term  Epizoa  has  been  applied  to  them  because  occurring 
on  the  exterior,  in  contradistinction  to  those  occurring  within 
animals,  which  are  called  Entozoa.  Some  of  them  are  classed 
with  insects,  as  having  six  legs;  while  others,  having  eight,  are 
called  Acari,  and  are  included  in  the  class  Arachnida. 

Some  very  minute  insects,  called  Aphides,  are  abundant  on 
plants,  the  leaves,  &c.,  of  which  they  destroy.  Others,  called 
Cynips,  are  the  cause  of  the  excrescences  on  the  leaves,  &c., 
of  trees,  termed  galls.  The  well-known  oak-apple  is  produced 
by  the  Cynips  quercus,  which  is  a  most  elegant  object  when 
examined  by  reflected  light.  The  same  may  also  be  said  of 
the  insect  from  the  gall  of  the  rose.  Gather  the  galls  when 
ripe,  and  place  them  in  a  box  covered  with  gauze.  In  a  few 
days  or  weeks  numbers  of  insects  will  escape  from  the  gall, 
and  those  exhibiting  beautiful  colours  may  be  selected. 

Among  the  Acari,  may  be  mentioned  the  cheese-mite,  A. 
domesticus,  and  the  itch-insect,  A.  scabiei.  To  obtain  the 
latter,  the  operator  must  examine  carefully  the  parts  surround- 
ing each  pustule,  and  he  will  generally  find  in  the  early  stage 
of  the  disease,  a  red  spot  or  line  communicating  with  it;  this 
part,  and  not  the  pustule,  must  be  probed,  and  the  insect,  if 
present,  be  turned  out.  It  is  often,  however,  difficult  to  de- 
tect its  haunts. 

To  obtain  the  Entozoon  folliculorum^  which  is  a  parasite 
occurring  in  the  sebaceous  follicles' of  the  skin  of  the  forehead, 
nose,  &c.,  squeeze  the  neighbourhood  of  the  little  black  spot 


PROCURING    OBJECTS.  83 

or  pustule,  so  as  to  force  out  the  sebaceous  or  oily  matter. 
This  should  be  laid  on  a  slide,  and  a  small  quantity  of  oil 
added  to  separate  the  insects  from  the  nidus  in  which  they  are 
imbedded.  They  may  then  be  transferred  by  a  pencil-brush 
to  a  clean  slide,  covered  with  thin  glass  and  mounted. 

Another  species  of  Acarus,  the  harvest-bug  or  tick,  A.  au- 
tumnalis,  is  a  very  painful  source  of  irritation  to  the  skin 
wherein  they  may  have  insinuated  themselves.  They  may  be 
dislodged  with  a  needle,  and  mounted  in  fluid  or  balsam. 

Tracheae  and  Spiracles  of  Insects. — The  respiratory  system 
of  insects  will  be  described  in  the  chapter  on  Dissections,  to- 
gether with  their  nervous,  digestive,  and  circulatory  systems. 
The  manner  of  mounting  them  is  alluded  to  on  page  60. 

Stings,  Ovipositors,  &c.,  frequently  require  considerable  care 
in  dissection.  They  may  be  mounted  in  fluid  or  balsam. 

SHELLS  OF  MOLLUSCA. — The  structure  of  shell  has  only 
lately  attracted  the  attention  of  microscopists,  but  since  the 
year  1842  the  subject  has  been  scientifically  investigated  by 
Mr.  Bowerbank  and  Dr.  Carpenter.  According  to  the  experi- 
ments of  the  latter  gentleman,  undertaken  at  the  request  and 
expense  of  the  British  Association,  the  calcareous  matter  in 
all  shells  is  nearly  equally  crystalline  in  its  aggregation,  and 
the  particular  forms  which  their  fracture  presents  are  deter- 
mined chiefly,  though  not  entirely,  by  the  arrangement  of  the 
animal  basis  of  the  shell,  which  possesses  a  more  or  less 
highly-organized  structure. 

All  thin  sections  of  recent  shell  are  translucent,  except 
when  the  colouring  matter  is  opaque,  or  when  the  calcareous 
matter  is  deposited  in  a  chalky  state  between  the  true  laminae 
of  the  shell,  as  in  the  oyster. 

Dr.  Carpenter  classifies  shells,  into — 1.  Prismatic  cellular 
structure,  as  exemplified  in  the  Pinnae.  2.  Membranous  shell 
substance,  as  the  My  a,  Anatina,  and  Thracia.  3.  Nacreous 


84  THE    MICROSCOPIST. 

or  pearl  structure,  as  the  inner  surface  of  some  species  of 
Ostrea  and  Mytilus.  4.  Tubular  structure,  as  the  outer  layer 
of  Anomia  EpJiippium,  Lima  scabra,  &c.  In  some  cases  the 
tubes  run  at  a  distance  from  each  other  obliquely  through  the 
shell,  as  in  Area  No&.  5.  Cancellated  structure.  Examples 
of  this  latter  division,  which  somewhat  resemble  the  cancelli 
of  bone,  are  only  met  with  in  certain  fossil  shells. 

Shell  should  be  examined  microscopically  in  three  ways :  by 
reflected,  transmitted,  and  polarized  light.  For  the  first,  frag- 
ments of  shell  will  suffice ;  for  the  others,  thin  sections,  cut 
both  vertically  and  transversely,  are  necessary.  To  exhibit  the 
animal  basis  of  shell,  specimens  may  be  treated  in  the  manner 
recommended  for  coral. 

SCALES  or  FISH. — M.  Agassiz  has  arranged  the  class  of 
fishes  into  four  orders,  according  to  the  structure  of  their 
covering,  as  follows : 

Enamelled  Scales. 

1.  Placo'idians.  Cartilaginous  fishes,  having  prickly  or  flat- 
tened spines,  as  the  skates,  dog-fish,  and  sharks. 

2.  Gano'idians.  With  angular  scales  composed  of  horny  or 
bony  plates  covered  with  enamel,  as  the  sturgeon,  and  bony 
pike.     Fifty  out  of  sixty  genera  are  extinct. 

Scales  not  Enamelled. 

3.  Cteno'idians.  Scales  notched  or  serrated  on  their  posterior 
free  edges,  as  the  perch. 

4.  Cycloid  fishes,  with  smooth  scales,  more  or  less  circular, 
and  laminated,  as  the  herring,  salmon,  &c. 

Among  the  various  kinds  of  fish-scales  selected  for  micro- 
scopic objects,  those  of  the  eel  are  much  prized,  as  it  was  for- 
merly considered  that  it  had  no  scales.  They  may  be  obtained 


PROCURING    OBJECTS.  85 

from  the  under  surface  of  the  skin  with  a  knife  or  a  pair  of 
forceps. 

Some  scales  when  viewed  by  polarized  light  have  a  brilliant 
effect.  They  may  be  mounted  in  balsam.  Fossil  scales,  as  well 
as  others,  may  be  examined  as  opaque  objects. 

HAIR  OF  ANIMALS,  &c. — Hairs  are  composed  of  an  aggre- 
gation of  epithelium  cells,  and  the  colour  depends  upon  the 
quantity  of  pigment  deposited  in  or  about  each  cell.  Care 
should  be  taken  to  select  both  the  hair  and  the  wool  from  each 
animal,  as  they  differ  materially  in  their  structure ;  the  finer 
kind,  or  what  is  known  as  wool,  being  endued  with  the  pro- 
perty termed  felting ,  which  property  is  of  considerable  impor- 
tance in  a  manufacturing  point  of  view. 

The  felting  property  is  owing  to  the  imbricated  scales  on 
the  outside  of  each  hair.  In  the  adult  human  hair  this  struc- 
ture is  not  very  apparent,  but  may  frequently  be  seen  in  fine 
specimens  from  very  young  infants.  These,  however,  should 
not  be  mounted  in  balsam. 

The  smaller  kind  of  hair  may  be  mounted  dry  or  in  fluid ; 
or,  if  of  a  dark  colour,  in  balsam.  Horizontal  and  vertical 
sections  should  be  made  of  large  hairs  and  spines,  which  may 
be  done  after  gluing  a  number  together,  in  the  same  way  that 
sections  of  wood,  &c.,  are  made. 

Sections  of  horns,  hoofs,  quills,  whalebone,  spines  of  echini, 
&c.,  are  all  interesting  objects. 


ANATOMICAL    OBJECTS    AND    PREPARATIONS. 

BLOOD. — To  examine  this  vital  fluid,  it  is  necessary  to  place 
upon  a  glass  slide  a  small  drop  recently  taken,  and  cover  it 
with  a  thin  glass  or  piece  of  mica.  The  blood  corpuscles  may 
also  be  preserved  in  Dr.  Groadby's  A  2  fluid,  or  prepared  by 


86  THE    MICROSCOPIST. 

drying  rapidly  on  the  slide  and  covering  with  the  thinnest 
glass. 

The  red  corpuscles  in  man  are  of  a  circular  flattened  form. 
If  water  be  added  to  them,  they  become  spherical  by  endos- 
mose.  Their  appearance  varies  as  they  are  viewed  a  little  in 
or  out  of  the  focus  of  the  microscope ;  in  one  place  showing  a 
nucleus  or  spot  in  the  centre,  and  in  the  other  a  thickened 
edge,  like  a  ring.  In  all  air-breathing,  oviparous,  vertebrated 
animals,  the  blood  corpuscles  are  oval,  and  a  nucleus  may  be 
observed  within  each  of  them.  This  nucleus  is  rendered  very 
distinct  by  the  addition  of  a  drop  of  diluted  acetic  acid. 

The  observations  of  Professor  Owen  on  the  blood-discs  of 
the  Siren  lacertina,  show  that  the  nucleus  consists  of  a  cluster 
of  nucleoli  enclosed  in  a  capsule  in  the  centre  of  the  oval 
blood-disc.  The  length  of  the  disc  in  the  Siren  is  4  j^th  of 
an  inch,  while  the  diameter  of  human  blood-discs  average 
•y^^th  of  an  inch. 

Circulation  of  Blood  may  be  seen  in  the  web  of  a  frog's 
foot  (see  page  46) ;  in  the  fin  or  tail  of  a  fish ;  and  in  the  legs, 
&c.,  of  many  spiders  and  insects,  especially  aquatic  larvae. 
There  is  nothing  so  wonderful  and  pleasing  as  the  sight  of  the 
blood  corpuscles  coursing  through  the  vessels  in  the  web  of  a 
frog's  foot,  when  seen  with  a  power  of  about  200  diameters. 
The  researches  of  Kaltenbrunner ;  a  distinguished  German  pa- 
thologist; on  the  circulation  of  blood  in  a  frog's  foot,  and  the 
influence  of  various  irritants  upon  it,  as  seen  under  the  micro- 
scope; have  added  much  to  our  knowledge  respecting  conges- 
tion and  inflammation,  and  are  of  the  highest  interest  to  the 
practitioner  and  student  of  medicine.  They  are  referred  to  by 
Dr.  Watson  in  his  preliminary  lectures  on  the  Practice  of 
Medicine,  and  their  importance  clearly  shown. 

BONE  should  be  cut  into  thin  sections,  about  ^th  of  an 
inch  in  thickness.  They  can  be  cut  with  a  fine  saw,  such  as 


PROCURING    OBJECTS.  87 

are  made  of  watchspring.  They  should  then  be  cemented  on 
a  piece  of  glass ;  filed  to  the  proper  thinness  ;  ground  upon  a 
hone ;  and  polished  by  a  leather  strap  or  piece  of  cloth  charged 
with  putty  powder  (oxide  of  tin  and  lead),  or  carbonate  of  iron 
(rouge).  They  may  be  mounted  dry  or  in  balsam.  Both 
transverse  and  longitudinal  sections  should  be  made. 

When  animal  tissues  are  consolidated  by  the  deposition  of 
earthy  matter  within  their  cells  and  fibres,  a  hard,  solid  sub- 
stance is  produced.  Sometimes  the  earthy  matter  crystallizes, 
as  in  the  teeth ;  at  other  times  it  combines  chemically  with 
the  gelatine  of  the  cells,  as  in  bone.  This  deposition  in  bone 

^does  not  occur  in  all  the  cells,  as  the  bone  requires  to  grow 
and  be  nourished;  hence  arises  its  peculiarity  of  structure. 
Independently  of  the  hollows,  or  cancelli,  the  hard  part  of 
the  bone  is  traversed  by  canals,  called  Haversian,  which  run 
in  the  direction  of  the  laminae ;  these  are  connected  by  trans- 
verse communications.  In  a  thin  transverse  section  of  bone, 
the  solid  matter  may  be  observed  arranged  around  the  Haver- 
sian canals  in  concentric  rows.  Among  these  layers  dark 
specks  are  dispersed.  These  dark  specks  (called  lacunae;  or 
corpuscles  of  Purkinje),  when  magnified  about  200  diameters, 
are  observed  to  be  cavities  of  an  irregular,  oval  form,  from 
which  emanate  numerous  minute  branch  canals.  These  cavi- 
ties appear  dark  for  the  same  reason  as  a  minute  air-bubble 
does  in  Canada  balsam — namely,  the  difference  of  refraction  of 
the  two  media.  By  means  of  these  branches  (canaliculi'), 
lacuna?,  and  Haversian  canals,  the  bone  is  nourished  with 
proper  fluids. 

It  has  been  shown  by  Mr.  J.  Quekett,  that  there  are  diffe- 
rences in  the  form  and  size  of  the  lacunae,  in  the  various  classes 
of  animals,  sufficiently  characteristic  to  allow  of  the  assignment 
of  minute  fragments  of  bone,  with  the  aid  of  the  microscope, 
to  their  proper  class.  The  lacunae  of  reptiles  are  distinguish- 


88  THE     MICROSCOPIST. 

able  by  their  large  size,  and  long  oval  form ;  and  those  of  fish, 
by  their  angular  form  and  the  fewness  of  their  radiating  cana- 
liculi.  The  lacunae  of  the  bird  may  be  distinguished  from 
those  of  the  mammal,  partly  by  their  smaller  size,  but  chiefly 
by  the  remarkable  tortuosity  of  their  canaliculi.  It  is  worthy 
of  remark,  also,  that  the  sizes  of  the  lacunae  in  the  four  classes 
of  vertebrata,  bear  a  close  relation  to  the  sizes  of  their  blood 
corpuscles. 

SECTIONS  OF  TEETH  may  be  made  in  the  same  way  as  bone. 
Some  should  be  soaked  in  hydrochloric  acid,  to  destroy  the 
earthy  matter,  and  others  in  caustic  potash,  to  get  rid  of  animal 
matter.  These  should  be  mounted  in  fluid,  the  others  dry,  or 
in  balsam. 

A  tooth  consists  of  three  distinct  structures,  the  relative  pro- 
portions and  arrangement  of  which  constitute  the  chief  differ- 
ences in  the  teeth  of  various  animals.  1.  Enamel.  This  is 
crystallized  phosphate  of  lime,  deposited  in  the  form  of  long 
prisms,  each  about  ^^th  of  an  inch  in  diameter,  produced  in 
animal  cells,  which  are  almost  obliterated  when  the  tooth  is 
fully  formed.  In  human  teeth  a  coating  of  enamel  is  formed 
over  the  crown  of  each.  In  the  teeth  of  some  animals  the 
enamel  is  disposed  in  vertical  layers  among  the  other  struc- 
tures of  the  tooth.  This  is  especially  the  case  with  the  grind- 
ing teeth  of  large  herbivorous  animals.  2.  Dentine,  or  Ivory. 
This  forms  the  principal  substance  of  which  the  teeth  are  com- 
posed. The  amount  of  animal  gelatine  in  it  is  often  very 
considerable.  The  earthy  matter  is  usually  deposited  in  the 
form  of  fine  branching  cylindrical  tubuli,  radiating  from  the 
centre  of  the  tooth.  These  tubules  have  been  successfully 
injected  with  colouring  matter  by  Dr.  "White,  of  Philadelphia. 
On  the  ends  of  the  dentine  tubuli  are  placed  the  ends  of  the 
enamel  prisms,  in  the  human  tooth*  Dentine  is  now  established 
by  Professor  Owen  as  an  ossification  of  the  pulp  of  the  tooth. 


PROCURING    OBJECTS.  89 

3.  The  Bone  or  Cementum,  of  teeth,  is  composed  of  a  mass 
of  earthy  matter  and  cartilage,  having  minute  cavities  or  bone 
corpuscles  and  calcigerous  canals. 

Sometimes  a  vertical  section  is  made  of  a  tooth  in  situ,  ex- 
hibiting a  section  of  the  jaw  with  its  cavities  for  the  nerves 
and  vessels,  as  also  the  manner  in  which  the  alveolar  process 
which  forms  the  socket  is  constructed.  Both  vertical  and  trans- 
verse sections  should  be  made. 

SKIN. — In  some  animals,  as  fish,  the  skin  is  not  very  vascu- 
lar, while  in  the  mammalia,  and,  perhaps,  in  the  human  subject, 
it  attains  the  highest  state  of  organization.  The  skin  performs 
a  function  in  the  animal  economy  second  only  in  importance 
to  that  of  the  lungs,  and  for  the  purpose  is  supplied  with  a 
very  rich  capillary  network;  and  also  provided  with  two  or 
more  sets  of  glands,  one  for  secreting  the  perspiratory  fluid, 
the  other  an  unctuous  or  sebaceous  matter  for  lubricating  the 
skin  itself.  Taking  the  human  skin  as  an  example,  we  should 
commence  the  study  with  vertical  sections,  made  through  parts 
supplied  both  with  hair  and  papillae.  The  perspiratory  glands 
are  best  seen  in  the  soles  of  the  feet,  and  palms  of  the  hands; 
the  sebaceous  glands  should  be  examined  in  parts  about  the 
face  or  chest,  where  hairs  are  numerous ;  these  latter  sections 
will  also  show  the  roots  of  the  hairs  and  the  hair  follicles. 
The  skin  may  be  rendered  firm  enough  for  vertical  section  by 
hardening  in  a  saturated  solution  of  carbonate  of  potash  or  in 
strong  nitric  acid.  The  capillary  network  of  the  cutis  vera 
may  be  seen  in  injected  specimens  when  the  cuticle  has  been 
removed,  which  will  often  require  the  aid  of  maceration  for 
the  purpose.  If  the  skin  be  that  of  a  black  man,  care  should 
be  taken  in  the  removal  of  the  cuticle,  as  in  it  may  be  ex- 
amined the  rete  mucosum,  or  coloured  layer,  which  consists  of 
a  series  of  minute  hexagonal  cells,  containing  pigment.  The 
same  structure  may  be  seen  in  the  skins  of  animals  whose 


90  THE    MICROSCOPIST. 

hairs  are  black ;  for  this  purpose  the  lips  of  a  black  kitten, 
when  injected,  should  be  selected,  as  in  them  the  mode  of 
growth  of  the  young  whiskers,  their  copious  supply  of  blood- 
vessels and  nerves,  and  various  other  points  of  interest,  may 
be  observed.  The  papillae  are  best  shown  in  the  extremities  of 
the  fingers  and  toes,  when  injected;  the  cuticle  which  invests 
them  should  also  be  mounted  as  an  object,  with  its  attached  or 
papillary  surface  uppermost,  as  in  this  the  grooves  for  their 
lodgment,  together  with  the  openings  of  the  sudoriferous 
glands,  can  be  well  seen. 

EYES. — Many  objects  of  interest  may  be  obtained  from  the 
eyes  of  various  animals ;  as  the  crystalline  lens,  the  pigment, 
the  ciliary  processes,  the  retina,  and  the  membrane  of  Jacob. 
The  structure  of  the  crystalline  lens  in  fish  is  best  seen  after 
the  lens  itself  has  been  hardened  by  drying,  boiling,  or  long 
maceration  in  spirit.  After  having  peeled  off  the  outside,  the 
more  dense  interior  will  be  found  to  split  up  into  concentric 
laminae,  and  each  lamina  will  also  be  found  to  be  composed  of 
an  aggregation  of  toothed  fibres ;  these  are  best  seen  when 
mounted  in  fluid,  but  if  dyed,  they  will  show  very  well  in 
balsam.  The  pigment  is  easily  obtained  by  opening  a  fresh 
eye  under  water.  It  may  then  be  detached  as  a  separate  layer, 
and  parts  of  it 'floated  on  slides  to  dry,  after  which  they  may 
be  mounted  in  balsam.  The  ciliary  processes  are  best  seen 
when  injected ;  they  should  be  mounted  in  a  convenient  cell 
with  fluid,  and  viewed  as  opaque  objects.  The  retina  should 
be  examined  from  a  very  fresh  eye,  between  glasses,  and  a 
little  serum  or  aqueous  humour  added,  to  allow  the  parts  to 
be  well  displayed;  but  water  must  be  avoided,  as  the  nervous 
matter  will  be  considerably  altered  by  it ;  the  membrane  of 
Jacob  will  also  require  the  same  precautions,  but  the  vascular 
layer  of  the  retina,  when  injected,  may  be  well  seen  after 
having  been  dried. 


PROCURING    OBJECTS.  91 

MUSCULAR  FIBRE. — Muscles  are  of  two  kinds,  voluntary 
and  involuntary;  from  their  functions.  The  voluntary  muscles 
of  all  the  vertebrata,  and  the  articulate  animals  (as  insects, 
&c.),  have  their  fibres  marked  with  transverse  striae.  The  in- 
voluntary muscles  are  not  so  marked.  These  marks  are  sup- 
posed to  point  out  the  ultimate  corpuscles  or  cells  of  which 
the  fibrillae  are  composed.  The  general  opinion  is,  that  the 
juxtaposition  of  cells  is  the  true  form  of  the  ultimate  fibre. 
Several  microscopists,  however,  of  some  note,  believe  the  fibre 
to  be  spiral,  and  enclosed  in  a  membranous  sheath.  In  my 
own  examinations  I  have  met  with  cases  where  the  structure 
appeared  to  be  a  bead-like  fibre  wound  spirally  into  a  tube,  or 
around  a  central  unmarked  fibre ;  yet  other  observations,  espe- 
cially with  polarized  light,  show  a  longitudinal  arrangement  of 
cells.  Perhaps  the  true  structure  is  a  compound  of  both  these 
modes ;  the  sheath  being  spiral,  and  the  ultimate  fibre  longi- 
tudinal. 

A  small  portion  of  muscle,  freed  from  cellular  tissue,  may 
be  put  on  a  slide  with  some  kind  of  fluid,  placed  under  the  dis- 
secting microscope,  and  the  fibres  torn  asunder  with  fine  needles. 
It  should  be  preserved  in  fluid  under  a  thin  glass  cover. 

The  nerves  of  muscle  may  be  displayed  in  a  thin  layer  of 
delicate  fibres  which  form  a  part  of  the  abdominal  wall  of  a 
frog,  by  employing  a  compressorium.  The  capillary  blood- 
vessels may  be  seen  when  injected,  in  the  thin  recti  muscles  of 
the  eyes  of  small  birds.  By  the  use  of  the  compressor,  these 
latter,  if  seen  soon  after  death,  will,  without  injection,  show 
both  nerves  and  capillaries. 

NERVE. — The  dissection  of  nerves,  to  show  their  ultimate 
structure,  is  similar  to  that  of  muscle,  above  described.  It 
should  be  performed,  however,  in  a  little  serum  or  white  of  an 
egg^  as  water,  &c.,  changes  its  appearance.  As  soon  as  the 
true  structure  has  been  well  seen;  water,  ether,  &c.,  may  be 


92  THE    MICROSCOPIST. 

added,  to  show  how  much  they  change  its  original  appearance. 
In  all  examinations  of  nerve  or  muscle ;  the  more  delicate  the 
structure,  the  sooner  after  death  should  it  be  dissected. 

FIBROUS  AND  AREOLAR  TISSUE. — Nearly  allied  to  involun- 
tary muscular  fibre  is  a  fibrous  tissue  termed  the  yellow  or 
elastic ;  this  is  often  found  in  connexion  with  another,  finer 
and  less  elastic,  and  called  from  its  colour,  the  white  fibrous 
tissue ;  a  mixture  of  the  two  is  known  to  anatomists  as  the 
areolar  tissue,  and  is  largely  used  in  the  animal  economy, 
as  it  forms  a  support  for  all  the  vessels,  nerves,  and  mus- 
cles, from  either  of  which  it  may  be  easily  procured.  The 
yellow  tissue  is  found  in  nearly  an  isolated  condition  in  the 
ligamentum  nuchse  of  the  necks  of  some  animals,  especially 
of  the  ruminating  tribe ;  it  also  enters  largely  into  the  forma- 
tion of  the  intervertebral  discs.  A  portion  of  the  ligament 
from  the  neck  of  a  sheep  or  calf,  even  after  boiling,  will  ex- 
hibit the  elastic  fibres  exceedingly  well ;  they  are  of  nearly 
uniform  size,  generally  curled  at  their  extremities,  and  of  a 
yellowish  colour.  They  may  be  prepared  as  muscle  or  nerve, 
with  the  needle  points. 

If  any  of  the  above  tissues  are  to  be  kept  they  should  be 
mounted  in  fluid,  as  spirit  and  water,  or  the  creasote  liquid. 

Mucous  MEkBRANE. — This  is  the  investment  of  all  the 
internal  parts  of  the  body,  continuous  with  the  skin.  Every 
cavity,  organ,  or  gland,  which  opens  on  the  surface,  is  lined  by 
it.  Shut  sacs  are  lined  by  serous  membrane. 

The  mucous  membrane  may  be  divided  into  two  parts  :  the 
epithelium,  and  the  basement  membrane.  The  external  skin 
is  evidently  a  similar  structure,  somewhat  modified,  and  is 
capable,  under  certain  circumstances,  of  taking  on  a  similar 
function.  The  epithelium  of  skin  is  the  cuticle  or  epidermis, 
but  the  basement  membrane,  though  present,  is  not  easily 
shown,  except  where  the  surface  is  raised  into  papillae. 


PROCURING    OBJECTS.  93 

The  epithelium  exists  in  three  varieties:  the  scaly,  pris- 
matic, and  spheroidal.  The  first  kind  is  most  largely  deve- 
loped in  the  skin ;  the  cuticle,  with  its  horns,  hairs,  hoofs,  and 
feathers,  &c.,  is  made  up  of  it.  Detached  scales  may  "be  ob- 
tained from  the  inner  side  of  the  mouth,  &c.  The  prismatic; 
or,  according  to  Dr.  Todd,  the  columnar;  is  abundant  throughout 
the  stomach  and  intestines,  and  even  the  lungs.  Each  prism 
is  attached  by  its  sides  to  its  fellows,  and  endwise  to  the  base- 
ment membrane.  The  attached  extremity  is  generally  pointed, 
the  free  one  wide  and  flat,  and  covered  with  vibratile  cilia, 
which  may  be  often  observed  in  rapid  motion,  some  time  after 
the  death  of  the  animal.  The  third  variety,  or  spheroidal,  is 
to  be  met  with  in  all  glandular  structures,  as  the  tubes  of  the 
stomach  and  kidney,  and  the  secreting  structure  of  the  liver. 

The  basement  membrane  is  structureless,  and  is  not  supplied 
in  any  way  with  vessels.  The  best  places  for  viewing  it  are 
the  tubes  of  the  kidney  and  stomach,  and  the  villi  of  the  small 
intestines.  It  is  supported  upon  a  submucous  areolar  tissue, 
in  which  both  the  blood  vessels  and  nerves  ramify,  but  do  not 
in  any  case  enter  the  mucous  membrane. 

In  order  to  examine  the  surface  of  mucous  membranes,  the 
mucus  should  be  washed  off  as  gently  as  possible,  by  a  small 
stream  of  water  or  a  small  syringe.  If  the  epithelium  be  re- 
quired, it  may  be  detached  from  the  surface  with  a  scalpel, 
placed  on  a  glass  slide,  and  viewed  as  a  transparent  object,  with 
a  power  of  200  diameters.  The  mucous  membrane  itself  may 
be  seen  by  reflected  light  while  under  water ;  a  movable  dis- 
secting microscope  being  brought  over  it.  In  order  to  obtain 
a  correct  idea  of  the  external  surface,  sections,  both  horizontal 
and  vertical,  should  be  taken  and  submitted  to  high  powers. 
When  the  membrane  cannot  be  well  cut  into  thin  slices,  it 
may  be  separated  with  the  needles,  or  by  slight  pressure  in 
the  compressorium.  Where  epithelium  is  so  abundant  as  to 


94  THE     MICROSCOPIST. 

form  a  layer  of  cuticle,  it  must  be  removed  by  maceration,  in 
order  to  see  the  mucous  surface. 

The  arrangement  of  the  capillaries,  as  seen  in  the  injected 
mucous  membranes,  is  exceedingly  interesting,  and  forms  a  nu- 
merous class  of  preparations. 

CILIARY  MOVEMENT. — If  the  roof  of  the  mouth  of  a  living 
frog  be  scraped  with  the  end  of  a  scalpel,  and  the  detached 
mucous  matter  placed  on  a  glass  slide,  and  examined  with  a 
power  of  200  diameters,  the  epithelium  cells,  and  the  move- 
ment of  their  cilia,  may  be  well  seen.  The  most  common 
method  is,  however,  to  cut  off  with  a  pair  of  fine  scissors  a 
small  portion  of  the  gills  (branchiae)  of  an  oyster  or  mussel ; 
lay  it  on  a  slide  or  on  a  tablet  of  an  animalcule  cage,  with  a 
drop  or  two  of  the  fluid  from  the  shell.  With  the  needle- 
points separate  the  filaments  from  each  other,  and  cover  it 
lightly  with  a  thin  piece  of  glass.  The  cilia  may  then  be  seen 
^n  several  rows,  beating  and  lashing  the  water  with  amazing 
activity.  If  fresh  water  be  added  instead  of  that  from  the 
shell,  the  movement  will  speedily  stop.  The  motion  and 
structure  of  the  cilia  is  sometimes  better  observed  after  the 
lapse  of  some  hours,  as  the  movement  will  then  have  become 
sluggish. 

INJECTED  PREPARATIONS. — We  have  already  referred  to 
the  arrangement  of  the  capillaries  in  mucous  membranes,  mus- 
cular tissue,  the  eye,  &c.  A  collection  of  such  preparations  is 
of  considerable  importance. 

There  can  be  no  doubt,  but  that  the  blood  is,  par  excellence, 
the  vital  fluid.  From  it  is  derived  the  material  for  the  deve- 
lopment of  each  part  of  the  organization ;  nerve,  as  well  as  mus- 
cle, bone,  tendon,  &c.  Even  unnatural  and  morbid  growths 
must  have  their  origin  in  some  alteration  in  this  all-pervading, 
all-sustaining  fluid.  "  The  life  thereof  is  the  blood  thereof." 

The  capillary  vessels  of  the  body  form  the  vehicle  of  vital 


PROCURING    OBJECTS.  95 

distribution  and  stimulus.  By  them  is  conveyed  the  nutrition 
of  all  the  tissues ;  and  through  them  all  foreign  substances  are 
extracted,  and  the  blood  thus  rendered  pure  and  vital.  By 
endosmotic  action  through  their  thin  coats  in  the  lungs,  oxy- 
gen unites  with  the  carbon,  and  probably  the  iron  of  the  blood, 
and  carbonic  acid  gas  is  expelled ;  and  from  their  peculiar  ar- 
rangement in  the  kidney,  lobules  of  the  liver,  &c.,  effete  mat- 
ters are  strained,  as  it  were,  from  the  circulation,  and  carried 
off. 

But  there  is  another  function,  of  equal,  if  not  superior,  im- 
portance with  those  just  mentioned,  which,  in  the  judgment  of 
the  author  of  this  work,  the  capillaries  are  destined  to  subserve. 
They  are,  doubtless,  the  cause,  perhaps  the  sole  cause,  of  the 
difference  in  the  sensations  experienced  in  the  various  organs 
and  tissues  of  the  animal  frame,  under  the  stimulus  of  the 
varied  excitants  to  which  the  organization  is  subject  in  health 
and  disease.  The  nervous  cords  may  transmit  impressions  to 
the  sensoriuin,  but  it  is  the  stimulus  of  the  blood — the  vital 
fluid — variously  modified  by  the  capillaries,  which  determines 
the  character  of  those  impressions.  Hence  we  find  that  those 
parts  which  are  but  slightly  supplied  with  capillary  vessels 
are  comparatively  dull  of  sensation,  and  vice  versa.  How 
otherwise  can  we  account  for  the  different  sensations  produced 
by  inflammation  in  different  tissues ;  as  for  instance,  the  burn- 
ing, pungent  pain  of  inflamed  skin,  contrasted  with  the  dull, 
aching  sensation  of  inflammation  in  the  fibrous  tissue. 

May  not  the  peculiar  and  delicate  arrangements  of  the  capil- 
laries in  the  different  coats  of  the  eye;  the  ear;  the  papillae 
of  the  skin ;  and  other  organs  of  special  sense ;  be  referred  to 
the  same  design  ? 

Other  physiological  facts  also  tend  to  establish  this  view. 
"If  the  abdominal  aorta  be  tied,  the  muscles  of  the  lower 
extremities  will  be  paralysed,  and  on  removing  the  ligature, 


96  THE    MICROSCOPIST. 

and  allowing  the  blood  to  flow,  the  muscles  will  recover  them- 
selves." (Todd  and  Bowman.}  We  know,  too,  that  the 
stimulus  of  too  much,  or  too  rapid,  blood  on  the  brain,  will 
produce  delirium,  and  illusions  of  special  sense": — impressions 
being  made  on  the  sensorium  independent  of  the  action  of 
usual  external  stimuli. 

The  theory  above  referred  to,  in  order  to  explain  or  account 
for  these  phenomena,  may  be  expressed  as  follows : — The 
principle  of  life,  or  the  capacity  for  vital  action,  is  a  property 
impressed  by  the  Great  Creator  upon  the  material  organization 
of  both  animals  and  vegetables.  In  addition  to  this,  the  pro- 
perties of  sensation  and  volition  have  been  imparted  to  all  ani- 
mals. These  properties  point  out  the  existence  of  a  spiritual 
being  or  entity  (distinct  from  vital  organization),  which  holds 
its  connexion  with  each  part  of  the  animal  frame  by  means  of 
the  nervous  system.  It  is,  however,  essential  to  the  integrity 
of  this  connexion,  and  to  the  proper  performance  of  the  func- 
tions of  volition  and  sensation,  that  the  nerves  should  be 
supplied  with  the  proper  vital  stimulus  of  the  organization — 
the  blood — and  the  mode  in  which  this  stimulus  is  supplied, 
will  determine  the  character  of  the  impressions  made  upon,  or 
received  by,  the  entity  or  being  referred  to. 

This  entity,  'which  some  have  confounded  with  the  vital 
principle,  acts  through  the  nerves  in  a  manner  peculiar  to  itself. 
The  force  or  material  by  which  it  holds  connexion  with  the 
bodily  frame  is  not  electricity,  although  in  some  respects  its 
properties  are  analogous.  Messrs.  Todd  and  Bowman  present 
the  following  arguments,  which  prove  conclusively  the  last 
remark.  They  show  that  the  electric  fluid  could  not  be  suffi- 
ciently insulated  in  the  minute  nerve-tubes  to  enable  them  to 
be  proper  conductors — that  the  most  delicate  tests  of  electri- 
city fail  to  discover  it,  when  applied  to  nerve  in  action — that  a 
ligature  to  a  nerve  stops  the  propagation  of  nervous  power,  but 


PROCURING    OBJECTS.  97 

not  of  electricity — that  if  a  piece  of  nerve  be  cut  out  and  be 
replaced  by  an  electric  conductor,  electricity  will  be  transmit- 
ted when  applied,  but  no  nervous  force  excited  by  stimulus 
above  the  section  will  pass  to  the  parts  below — and  that  both 
nerve  and  muscle  are  infinitely  worse  conductors  of  electricity 
than  copper  or  other  metals.  These  facts  are  clearly  opposed 
to  the  present  popular  theory  of  the  identity  of  nervous  force 
and  electricity. 

More  extended  remarks  upon  our  theory  of  the  cause  of 
sensations  would  be  out  of  place  in  a  work  of  this  kind ;  yet  as 
the  varied  shapes  and  arrangement  of  the  capillaries  must  be 
demonstrated  by  means  of  the  microscope,  and  as  we  have 
seen  no  theory  which  attempts  to  explain  the  design  of  such 
variations,  an  allusion  to  this  seemed  to  be  appropriate. 

It  may  be  mentioned,  however,  that  this  view  will  throw 
great  light  upon  the  cause  and  cure  of  insanity,  as  well  as  other 
diseases;  and  upon  the  modus  operandi  of  many  articles  of 
the  materia  medica.  It  is,  indeed,  a  question  worthy  to  be 
entertained,  whether  diseases,  which  are  so  clearly  divisible 
into  sthenic  and  asthenic,  may  not,  after  all,  chiefly  result 
from  an  alteration  of  tone  or  capacity  in  the  capillaries  of  an 
organ,  tissue,  or  of  the  whole  system.  Cullen's  idea,  that 
fever  is  caused  by  a  spasm  in  the  capillaries,  may  not  be  far 
from  the  truth,  though  it  be  but  a  theory. 

To  sum  up  all  which  our  present  limits  will  allow;  the 
capillaries  are  the  most  interesting  and  important  vessels  of  the 
body,  and  yet,  perhaps,  the  least  studied.  A  work  specially 
devoted  to  them — their  description  and  properties — would  be 
a  valuable  accession  to  physiological  science. 


CHAPTER   VII. 

TEST    OBJECTS. 

THE  discovery  of  this  class  of  objects  by  Dr.  Goring,  a  full 
account  of  which  may  be  found  in  Mr.  Pritchard's  works  on 
the  Microscope,  was  the  chief  cause  of  the  modern  improve- 
ments in  the  achromatic  compound  microscope. 

Mr.  Pritchard,  following  Dr.  Goring,  divides  test  objects 
into  two  classes,  viz.,  tests  of  the  penetrating  power,  and  tests 
of  the  denning  power  of  the  instrument;  the  first  showing  its 
destitution  of  spherical  and  chromatic  aberration,  and  mechani- 
cal imperfection;  and  the  other  class  showing  its  angle  of 
aperture. 

This  distinction  is  not  now  necessary,  as  few  persons,  save 
those  engaged  in  the  manufacture  of  object-glasses,  attend  to 
the  former,  the 'improvement  in  achromatic  object-glasses  hav- 
ing been  so  extensive  that  a  good  instrument,  in  this  respect, 
is  readily  procurable.  Still,  it  may  be  well  to  give  an  outline 
of  the  means  by  which  the  presence  or  absence  of  achromati- 
city  may  be  known. 

Chromatic  aberration  is  rendered  sensible  by  almost  any 
transparent  object,  when  the  light  falls  upon  it  obliquely;  but 
more  especially  by  such  as  are  not  transparent,  but  only  illu- 
minated by  intercepted  light,  of  which  a  very  good  example 
may  be  seen  in  a  piece  of  fine  wire  sieve,  treated  like  a  dia- 
phanous object,  also  in  a  thin  plate  of  metal  perforated  by  very 


TEST    OBJECTS.  99 

small  holes.  The  various  colours  are  seen  according  to  the 
order  of  their  refrangibility,  by  putting  the  object  both  within 
and  without  the  focus,  as  well  as  by  viewing  it  at  the  focal  point. 

Spherical  aberration  is  most  sensibly  felt  in  viewing  opaque 
objects,  especially  if  of  the  brilliant  class.  It  shows  itself  in 
a  variety  of  ways :  first,  as  a  diffused  nebulosity  over  the  whole 
field  of  view;  secondly,  as  a  confined  nebulosity,  extending 
only  to  a  certain  distance  from  the  object;  and  thirdly,  in  a 
want  of  sharpness  and  decision  in  the  outline  caused  by  a 
penumbra  or  double  image,  which  can  never  be  made  to  lap 
perfectly  over  the  stronger  or  true  one.  Destitution  of  spheri- 
cal aberration  is  evinced  by  the  absence  of  these  appearances, 
and  by  the  vanishing  of  the  image  immediately  that  the  object 
is  put  out  of  focus  either  way. 

To  ascertain  the  defects  alluded  to  above,  a  minute  globule 
of  mercury  on  a  black  ground,  known  as  an  "  artificial  star," 
is  used.  It  presents  a  very  minute  point  of  light.  Very  mi- 
nute globules  of  mercury,  spread  over  a  blackened  surface,  are 
viewed  as  opaque  objects,  being  illuminated  by  the  light  from 
a  window  or  lamp  thrown  on  them  by  a  condensing  lens. 
When  one  of  these  globules  is  in  the  focus  of  a  single  lens 
object-glass,  a  strong  coma  surrounds  the  miniature  image  of 
the  window  seen  in  the  globule,  and  when  within  or  without 
the  focus,  the  light  of  the  window  swells  out  into  a  circular 
disc.  These  appearances  are  more  or  less  accompanied  by 
prismatic  colours. 

When  an  achromatic  combination,  perfectly  corrected  for 
both  kinds  of  aberration,  is  employed,  the  globule  should  ex- 
hibit similar  appearances  both  within  and  without  the  best 
focus ;  and  when  at  the  ftfcus,  the  point  of  light  should  be  seen 
as  a  minute  disc,  free  from  irradiations  and  colour,  except  a 
general  blueness,  which  results  from  the  irrationality  of  the 
spectra  of  the  different  glasses  of  which  the  object-glass  is 
composed. 


100  THE    MICROSCOPIST. 

Power  of  definition  depends,  in  a  great  measure,  upon  the 
angle  of  aperture  of  the  object-glass.  A  deficiency  of  angular 
aperture  is  shown  by  a  want  of  light,  producing  unsatisfactory 
vision,  which  is  rather  increased  than  ameliorated  by  augment- 
ing the  intensity  of  the  artificial  illumination;  by  an  incapa- 
city of  showing  lined  objects,  except  such  as  are  of  the  lowest 
class ;  and  by  giving  very  large  spurious  discs  with  artificial 
stars ;  also  by  showing  easy  test  objects  with  the  lines  faint, 
while  the  spaces  between  them  are  darker  and  more  opaque 
than  they  ought  to  be. 

When  the  aberrations  are  properly  corrected,  and  the  angle 
of  aperture  considerable,  the  lines  on  test  objects  become  fine, 
sharp,  and  dark,  and  the  spaces  between  them  bright,  pro- 
vided the  illumination  has  been  properly  conducted;  they 
moreover  become  visible  in  a  very  faint  light ;  the  outline  and 
the  lines  are  seen  at  once ;  and  the  spurious  discs  of  all  bril- 
liant points  are  very  sharp  and  small. 

In  order  to  explain  more  fully  what  is  meant  by  angular 
aperture,  let  A  and  a,  Figs.  23  and  24,  represent  two  objects, 
in  all  respects  alike ;  and  suppose  B,  B,  and  5,  6,  to  be  two 
object-glasses  of  equal  focal  length;  the  former  a  single  lens, 
of  the  best  construction,  such  as  was  used  in  the  old  compound 
microscope,  and*  the  latter  a  lens  of  the  newest  form,  termed 
an  achromatic.  Now  these  object-glasses  will  form  their  re- 
spective images  at  I  and  i,  and  they  will  be  of  equal  dimen- 
sions. But  if  the  number  of  rays  proceeding  from  A  and 
falling  upon  the  single  lens  B,  B,  is  not  enough,  when  col- 
lected at  I,  sufficiently  to  stimulate  the  eye,  any  minute  pore, 
stria,  or  other  marking  at  A,  will  not  be  rendered  visible; 
while  from  the  increase  of  aperture  in  &,  b,  allowing  much 
more  light  to  be  transmitted,  every  mark  at  a  will  be  repre- 
sented at  ij  and  the  eye  being  powerfully  acted  on  by  the 
increase  of  light,  will  be  highly  sensible  of  it. 


TEST    OBJECTS. 


101 


The  angles  B,  A,  B,  and  5,  a,  b,  are  the  angles  of  aperture 
of  the  respective  object-glasses,  and  the  quantity  of  light 
transmitted  will  be  as  the  squares  of  B,  B;  and  5,  6,  their  focal 
length  being  equal. 


Fig.  24. 


It  may  be  supposed,  that  if  we  throw  more  light  upon  an 
object,  so  that  more  may  be  collected  by  the  object-glass,  we 
shall  be  better  able  to  define  its  structure;  and  this  would 
probably  be  the  case  if  we  could  throw  light  only  upon  those 
minute  parts  which  we  wish  to  examine,  and  not  upon  the 
whole  object,  but  as  we  cannot  increase  the  relative  propor- 
tions of  light,  the  advantages  proposed  cannot  be  derived. 


102  THE    MICROSCOPIST. 

In  examining  test  objects  it  will  be  well  to  remember  that 
there  are  generally  some  very  easy  ones,  even  among  samples 
of  the  most  difficult  kind.  The  darker  the  specimen,  the  more 
easily  is  it  made  out  j  and  the  more  transparent  the  tissue,  the 
greater  difficulty  there  is  in  developing  its  structure.  Great 
attention  too  should  be  paid  to  the  proper  illumination  of  the 
object,  or  a  superior  instrument  will  be  undervalued. 

The  following  list  affords  an  account  of  those  objects  most 
frequently  used  as  tests  of  the  defining  power  of  the  instrument. 

BAT'S  HAIR. — This  is  a  most  beautiful  structure,  presenting 
a  series  of  scale-like  projections  arranged  in  the  form  of  a 
whorl  around  the  central  part  or  shaft.  They  are  least  nume- 
rous at  the  base  of  the  hair,  and  increase  towards  the  apex. 

MOUSE  HAIR  differs  materially  from  the  other  in  size  and 
structure.  Their  internal  structure  is  cellular,  there  being 
three  or  more  rows  of  cells  in  each  hair,  the  colour  of  the  hair 
depending  on  the  pigment  within  the  cells.  Under  the  micro- 
scope all  hairs  should  have  their  light  or  transparent  parts 
clearly  and  distinctly  separated  from  the  darker  portions,  and 
it  is  from  the  sharpness  with  which  the  parts  are  separated 
that  a  correct  opinion  of  the  value  of  an  instrument  can  be 
obtained. 

In  selecting  hair  of  animals  for  examination,  the  lightest 
coloured  should  be  preferred.  Like  the  scales  on  insects,  the 
hair  from  different  parts  of  the  same  individual  varies  con- 
siderably in  structure. 

HAIR  or  THE  DERMESTES. — This  very  remarkable  hair  is 
obtained  from  the  larva  of  a  small  beetle,  which  preys  on  dried 
animal  substances,  as  bacon  and  hams.  It  is  covered  with 
brownish  hairs,  the  longest  of  which  are  selected. 

The  shaft  of  this  hair  is  covered  with  whorls  of  close-set 
spines,  and  at  the  head  is  invested  with  a  curious  arrangement, 
consisting  of  several  large  filaments  or  spines,  which  are 


TEST    OBJECTS.  103 

pointed  at  their  distal  extremities,  and  provided  with  a  pro- 
tuberance at  their  proximal  ends. 

This  object,  with  the  others  above  noticed,  is  a  good  test  of 
the  defining  power  of  a  half-inch  object-glass. 

SCALES  or  INSECTS. — The  dust  on  the  wings  and  bodies  of 
butterflies,  moths,  and  other  insects,  prove,  on  microscopic  ex- 
amination, to  be  scales  or  feathers,  overlapping  each  other  like 
the  shingles  on  the  roof  of  a  house.  They  vary  much  in  form 
and  size ;  and  from  the  difficulty  of  developing  their  structure, 
they  form  excellent  test  objects.  In  the  present  list  the  most 
easy  are  first  named. 

Lepisma  Saccharina. — These  silvery-scaled  insects  frequent 
closets,  book-shelves,  &c.,  and  are  very  common.  Their  scales 
are  very  pretty  objects,  but  are  so  easily  made  out  as  hardly  to 
deserve  the  name  of  test  objects.  The  longitudinal  striae 
appear  to  stand  out  in  bold  relief,  like  the  ribs  of  a  shell.  A 
good  glass  should  show  well  the  contrast  between  the  striae  and 
the  interspaces. 

Morplio  Menelaus. — The  pale  blue  scales  from  the  upper 
surface  of  the  wing  of  this  splendid  butterfly  form  a  good 
test  for  the  half-inch  object-glass,  which  should  show  clearly 
the  transverse  as  well  as  the  longitudinal  strise,  giving  it  a 
brickwork  appearance.  If  the  scale  be  flat,  which  is  not  com- 
mon, the  strise  should  be  seen  over  the  whole  surface.  Some- 
times the  scales  are  damaged,  the  pigment  having  been  re- 
moved; in  such  cases  the  cross  striae  cannot  be  seen.  The  pig- 
ment, under  very  high  powers,  exhibits  a  dotted  appearance 
between  the  strise. 

Tinea  Vestianetta,  or  Clothes  Moth. — The  scales  of  these 
insects  are  very  delicate,  and  require  some  tact  in  the  manage- 
ment of  the  illumination  to  resolve  their  lines  distinctly.  The 
small  scales  from  the  under  side  of  the  wing  should  be  taken; 
the  others  are  easy. 


104  THE    MICROSCOPIST. 

Poutia  Brassica,  or  Common  Cabbage  Butterfly. — The  pale, 
slender,  double-headed  feathers,  having  brush-like  appendages 
at  their  insertion,  are  good  test  objects.  The  specimens  which 
are  easily  resolved  are  short,  broad,  and  more  opaque.  The 
striae  are  longitudinal,  and  with  a  power  of  500  diameters  ap- 
pear to  be  composed  of  rows  of  little  squares  or  beads. 

Podura  plumbea,  or  Lead- Coloured  Springtail. — The  body 
and  legs  of  these  tiny  creatures  are  covered  with  scales  of 
great  delicacy.  The  surface  of  each,  under  a  power  of  500 
diameters,  appears  covered  with  numbers  of  delicate  wedge- 
shaped  dots  or  scales,  arranged  so  as  to  form  both  longitudinal 
and  transverse  wavy  markings.  A  very  small  scale  is  a  good 
test  of  the  denning  power  of  a  one-twelfth  or  one-sixteenth- 
inch  object-glass.  The  small  scales  may  easily  be  rubbed  off 
the  scale  to  be  examined,  unless  great  care  be  taken  in  mount- 
ing, &c.,  and,  of  course,  it  will  be  useless  as  a  test  object. 

SHELLS  OF  INFUSORIA, — Several  delicate  species  serve  as 
test  objects.  The  so-called  longitudinal  and  transverse  striae 
are  resolved  by  superior  instruments  into  dots  or  bead-like 
projections  from  the  surface.  The  Navicula  hippocampus,  N. 
angulata,  N.  Spenccrii,  &c.,  have  been  recommended  as  tests. 
A  species  marked  Navicula  attenuata,  is  a  good  object,  re- 
quiring delicate,  illumination  under  a  high  power,  in  order  to 
show  the  longitudinal  striee  or  dots.  Several  kinds  of  Tripoli 
may  also  be  used  for  the  purpose. 

As  it  is  always  a  tedious  matter  with  the  use  of  a  high 
power  to  find  a  minute  object  on  the  slide  under  the  stage,  it 
will  be  most  convenient  to  bring  it  first  into  the  centre  of  the 
field  by  the  use  of  a  lower  power,  and  afterwards  substitute  the 
high  power  object-glass. 


CHAPTER   VIII. 

ON    DISSECTING    OBJECTS    FOR    THE    MICROSCOPE. 

^REFERENCE  has  already  been  made  in  Chapter  V.  to  the 
manner  of  dissecting  and  preparing  certain  animal  and  vege- 
table tissues,  yet  much  has  been  omitted,  which  may  perhaps 
be  more  fully  appreciated  under  the  present  head. 

The  instruments  required  in  microscopic  dissections;  or  mi- 
nute anatomy;  are  various  kinds  of  forceps,  scissors,  scalpels, 
needles,  troughs,  loaded  corks,  and  arm-rests. 

The  forceps,  in  addition  to  the  ordinary  forceps  used  in 
coarse  or  rough  dissection,  may  be  made  with  closely-fitting, 
sharp  points.  The  scissors  are  similar  to  those  used  for  surgi- 
cal purposes.  It  is  useful  to  have  a  pair  with  the  point  of  one 
of  its  blades  blunt  and  truncated,  for  cutting  open  tubular 
parts,  as  the  alimentary  canal.  Scissors  with  curved  blades 
are  also  of  service.  A  pair  of  very  small  scissors,  whose 


Fig.  25. 


blades  are  kept  open  by  a  spring,  a,  Fig.  25,  was  much  used 
by  Swammerdam  in  his  dissections.     One  of  the  handles  is 


106 


THE     MICROSCOPIST. 


attached  to  a  piece  of  wood,  b ;  the  other  is  curved  as  at  e,  in 
order  to  be  pressed  upon  by  the  thumb  or  forefinger  in  the  act 
of  cutting. 

The  ordinary  scalpels  or  knives  are  usually  too  large  for  all 
purposes ;  those,  however,  which  are  used  in  operations  on  the 
eye  will  be  of  service. 

For  making  fine  sections,  a  scalpel  or  a  razor  may  be  em- 
ployed, but  for  soft  substances,  as  the  liver,  spleen,  and  kid- 
Fig.  26. 


ney,  a  knife  with  two  parallel  blades,  called  Valentin's  Knife, 
Fig.  26,  may  be  used  with  advantage.  Dissecting  needles 
may  be  straight  or  curved.  One  of  the  latter,  fixed  in  a  pro- 
per handle,  is  represented  in  Fig.  27.  These  are  very  service- 
able instruments  for  separating  or  tearing  asunder  delicate 
tissues. 

Fig.  27. 


As  most  dissections  are  made  under  water,  convenient  troughs 
are  necessary.  They  may  be  from  two  inches  to  a  foot  long 
and  of  a  proportionate  breadth  and  depth.  Earthenware,  or 
glass,  is  the  best  material. 

Loaded  corks  are  flat  pieces  of  cork  covered  on  their  under 
surface  with  sheet  lead,  so  that  they  may  readily  sink  in  the 
water.  To  these  corks  the  subject  to  be  dissected  is  fastened 
with  pins. 


DISSECTING    OBJECTS.  107 

Rests  are  inclined  planes  of  wood;  one  on  each  side  of  the 
trough  holding  the  specimen.  If  the  Dissecting  Microscope 
represented  by  Fig.  5,  is  used,  neither  rests  nor  troughs  will 
be  required,  other  than  are  furnished  with  the  instrument; 
unless  it  be  troughs  for  specimens  not  immediately  under  exa- 
mination. 

In  addition  to  these  instruments,  a  small  syringe,  camel7 s- 
hair  pencil  brushes,  &c.  &c.,  will  be  found  useful. 

The  following  account  of  Swammerdam's  dissections  com- 
mends itself  to  all  microscopists.  It  is  condensed  from  an 
extract  in  Adams's  Essays,  from  Boerhaave's  Life  of  Swam- 
merdam. 

In  the  preparation  of  objects,  no  man  was  ever  more  suc- 
cessful or  more  indefatigable  than  Swammerdam.  His  chief 
art  seems  to  have  been  in  constructing  very  fine  scissors,  and 
giving  them  an  extreme  sharpness ;  these  he  made  use  of  to 
cut  very  minute  objects,  because  they  dissected  them  equally, 
whereas  knives  and  lancets,  if  ever  so  fine  and  sharp,  are  apt 
to  disorder  delicate  substances.  His  knives,  lancets,  and  styles, 
were  so  fine  that  he  could  not  see  to  sharpen  them  without  a 
magnifying  glass. 

He  was  also  dexterous  in  the  management  of  small  glass 
tubes,  which  were  no  thicker  than  a  bristle,  and  drawn  to  a 
fine  point  at  one  end,  but  thicker  at  the  other.  These  he  made 
use  of  to  show  and  blow  up  the  smallest  vessels  discoverable 
by  the  microscope ;  to  trace,  distinguish,  and  separate  their 
courses  and  communications,  or  to  inject  them  with  subtile 
liquors. 

He  used  to  suffocate  insects  in  spirits  of  wine  or  turpentine, 
and  likewise  preserved  them  some  time  in  these  liquids;  by 
which  means  he  kept  the  parts  from  decomposition,  and  added 
to  them  such  strength  aud  firmness  as  rendered  the  dissections 
more  easy.  When  he  had  divided  transversely  the  little 
creature  he  intended  to  examine,  and  carefully  noted  every- 


108  THE     MICROSCOPIST. 

thing  that  appeared  without  further  dissection,  he  then  pro- 
ceeded to  extract  the  viscera  in  a  very  cautious  and  leisurely 
manner;  first  taking  care  to  wash  away  and  separate,  with 
fine  pencils,  the  fat  with  which  insects  are  plentifully  sup- 
plied. 

Sometimes  he  put  into  water  the  delicate  viscera  of  the 
insects  he  had  suffocated;  and  then  shaking  them  gently,  he 
procured  himself  an  opportunity  of  examining  them,  especially 
the  air-vessels  and  trachea,  which  by  this  means  he  could 
separate  from  all  the  other  parts.  Again,  he  has  frequently 
made  punctures  in  other  insects  with  a  needle,  and  after 
squeezing  out  all  their  moisture  through  the  holes  made  in 
this  manner,  he  filled  them  with  air,  by  means  of  slender  glass 
tubes,  then  dried  them  in  the  shade,  and  anointed  them  with  oil 
of  spike,  by  which  means  they  retained  their  proper  forms  for  a 
long  time.  He  had  a  singular  secret  whereby  he  could  pre- 
serve the  nerves  of  insects  as  limber  and  perspicuous  as  ever 
they  had  been.  Some  insects  he  injected  with  wax  instead  of 
air. 

He  discovered  that  the  fat  of  all  insects  was  perfectly  solu- 
ble in  oil  of  turpentine ;  thus  he  was  enabled  to  show  the 
viscera  plainly,  only  after  this  operation  he  used  to  cleanse  and 
wash  them  well  and  often  in  water.  He  frequently  spent 
whole  days  in  thus  cleansing  a  single  caterpillar  of  its  fat,  in 
order  to  discover  the  true  construction  of  this  insect's  heart. 

His  singular  sagacity  in  stripping  off  the  skin  of  caterpillars 
that  were  on  the  point  of  spinning  their  cones  deserves  notice. 
This  he  effected  by  letting  them  drop  by  their  threads  into 
scalding  water,  and  suddenly  withdrawing  them ;  for  by  this 
means  the  epidermis  peeled  off  very  easily;  and  when  this  was 
done,  he  put  them  into  distilled  vinegar  and  spirit  of  wine, 
mixed  together  in  equal  proportions,  which,  by  giving  a  proper 
firmness  to  the  parts,  afforded  an  opportunity  of  separating 


DISSECTING    OBJECTS.  109 

them,  with  very  little  trouble,  from  the  exuviae,  or  skins,  with- 
out any  danger  to  the  parts ;  so  that  by  this  contrivance  the 
pupa  could  be  shown  to  be  wrapped  up  in  the  caterpillar,  and 
the  butterfly  in  the  pupa. 

Those  who  look  into  the  works  of  Swammerdam,  will  be 
abundantly  gratified,  whether  they  consider  his  immense  la- 
bour and  unremitting  ardour  in  these  pursuits,  or  his  wonder- 
ful devotion  and  piety.  On  one  hand,  his  genius  urged  him 
to  examine  the  miracles  of  the  Great  Creator  in  his  natural 
productions ;  while,  on  the  other,  the  love  of  that  same  All- 
perfect  Being,  rooted  in  his  mind,  struggled  hard  to  persuade 
him  that  Grod  alone,  and  not  his  creatures,  was  worthy  of  his 
researches,  love,  and  attention. 

To  render  this  section  more  perfect,  a  few  further  remarks 
on  the  internal  anatomy  of  insects  will  not  be  out  of  place. 
For  the  anatomy  of  other  parts  of  the  animal  organization,  the 
reader  is  referred  to  Chapter  V.,  and  the  usual  text  books. 

1.  Tracheae,  or  Respiratory  System  of  Insects. — Respiration 
in  insects  is  effected  by  means  of  two  great  longitudinal  ves- 
sels or  canals  called  tracheae,  running  along  the  sides  of  the 
body  beneath  the  outer  integuments  and  muscles,  terminating 
in  breathing  pores  (spiracles  or  stigmata).  These  pores  or 
spiracles  are  placed  along  each  side  of  the  body  in  terrestrial 
insects,  and  are  furnished  with  a  beautiful  mechanism  to  pre- 
vent the  admission  of  foreign  particles.  The  tracheae  emit  an 
infinite  number  of  ramifications,  extending  to  all  parts  of  the 
body,  so  that  air  circulates  freely  in  every  part.  The  tracheae 
consist  of  an  elastic  spiral  cartilage  rolled  up  into  a  tube, 
lined  on  each  side  with  cellular  tissue,  In  Fig.  28  the  tracheae 
of  the  larva  of  the  Cossus  liyniperda,  or  willow  moth,  is  re- 
presented. Along  each  side  of  the  caterpillar  are  seen  the 
spiracles. 

To  obtain  the  tracheae,  &c.,  the  insect  should  be  placed  in  a 

10 


110 


THE    MICROSCOPIST. 


small  trough  with  water,  and  be  securely  fixed  to  a  loaded  cork. 
The  body  being  laid  open,  next  to  the  large  viscera,  the  tra- 
cheae will  become  visible.  The  stomach  and  intestinal  canal, 
if  large  and  transparent,  will  exhibit  the  minute  ramifications 


Fig.  28. 


of  the  tracheae*  the  best;  for  this  purpose,  after  being  slit 
open  and  well  washed,  they  should  be  either  mounted  in  fluid 
or  be  placed  on  a  slide  to  dry.  If  care  be  taken  in  the  mount- 
ing, they  will  show  very  well  in  balsam.  When  the  entire 
tracheal  system  is  required  to  be  dissected  from  the  larva  of 
an  insect,  all  the  viscera  should  be  taken  out;  the  main 
trunks  with  their  tufts  of  branches,  will  then  be  seen  running 
down  on  either  side  of  the  body,  and  if  care  be  taken  in  the 
dissection,  the  whole  system  may  be  removed  from  the  cavity, 
and  laid  out,  or  rather  floated  on,  a  slide  to  dry,  previous  to 
being  mounted  in  balsam.  The  spiracles  require  very  little 


DISSECTING    OBJECTS. 


Ill 


dissection.  They  may  be  cut  from  the  body  with  a  scalpel  or 
pair  of  scissors,  and  be  mounted  in  fluid  or  in  balsam. 

2.  The  Digestive  System  consists  of  the  pharynx;  the  eso- 
phagus, or  gullet ;  the  craw,  or  crop ;  the  gizzard,  or  ventri- 
culus ;  the  stomach,  or  duodenum ;  the  intestines ;  and  a 
number  of  slender  membranous  tubes  filled  with  a  fluid 
analogous  to  bile.  In  addition  to  these,  the  salivary  glands 
may  be  mentioned. 

There  is  very  great  variety  in  the  digestive  apparatus  of 
insects.  In  those  which  feed  on  flesh,  the  alimentary  canal  is 
short,  as  in  the  higher  animals,  and  in  the  vegetable  eaters  it 

Fig.  29. 


is  long.  There  are  also  differences  of  structure,  which  clearly 
show  the  adaptation  of  means  to  ends.  A,  Fig.  29,  is  the 
digestive  system  of  Melolontha.  B,  is  that  of  Blatta  Ameri- 


112  THE     MICROSCOPIST. 

cana  (American  Cockroach),  a  is  the  esophagus,  b  the  crop,  at 
the  bottom  of  which  is  the  gizzard,  c,  consisting  of  several 
teeth  arranged  like  a  funnel,  with  the  apices  of  the  teeth  in 
the  centre.  Another  view  of  the  gizzard  is  seen  at  C.  The 
bile-tubes  or  liver  are  shown  at  dj  and  the  salivary  glands  at  e. 
Attached  to  the  stomach,  just  below  the  gizzard,  are  eight 
blind  sacs,/,  the  use  of  which  is  unknown,  but  is  supposed 
to  be  analogous  to  the  pancreas. 

The  salivary  glands,  stomach,  &c.,  should  be  generally 
mounted  in  fluid.  Gizzards  may  be  put  up  in  balsam.  The 
gizzard  of  a  cricket  is  an  interesting  object;  it  has  over  two 
hundred  teeth. 

3.  The  Nervous  System  consists  of  two  medullary  cords  or 
threads,  which  run  along  the  middle  of  the  abdomen  inside, 
exhibiting  a  series  of  knots  or  ganglia. 

Fig.  30  exhibits  the  nervous  system  of  a  caterpillar,  from  a 
preparation  of  Dr.  Goadby's.  The  double  ganglion,  A,  seems 
to  occupy  the  place  of  the  cerebellum,  and  B,  also  double,  and 
transverse  to  the  others,  answers  to  the  cerebrum.  C,  C,  the 
two  cords  uniting  them.  E,  the  space  through  which  the 
esophagus  passes.  F,  F,  F,  the  ganglia  which  unite  the  two 
cords.  The  distribution  of  the  nerves  through  the  body  is 
from  the  ganglia,.  The  apparent  exceptions  to  this,  as  at  D, 
are  proven,  by  Dr.  Goadby's  investigations  on  the  Limulus,  to 
be,  in  fact,  arteries,  as  they  have  been  injected.  Coagulated 
insect  blood  is  white,  hence  they  appear  like  nerves. 

4.  The  Circulatory  System  is  placed   along  the  back,  and 
consists  of  a  heart  or  dorsal  vessel ;   which  is  a  tube  divided 
into  chambers,  separated  from  each  other  by  valves.    There  are 
also  valves  at  the  sides  to  receive  the  blood  from  the  venous 
sinuses  of  the  body.    But  a  single  artery  has  been  seen,  which 
goes  to  the  head,  dividing  into  three  branches.    It  was  thought 
that  the  blood  exuded  through  the  vessel  and  found  its  way 
through  the  body  as  it  best  could,  back  to  the  heart ;  but  in 


DISSECTING    OBJECTS. 


113 


dissecting  a  Limulus  (king-crab),  Dr.  Goadby  traced  the  artery 
into  certain  large  sacs  or  vessels,  evidently  answering  the  pur- 
pose of  veins  (venous  sinuses).  It  is  probable  the  same  holds 


Fig.  30. 


Fig.  31. 


good  of  insects.  Fig.  31  represents  the  dorsal  vessel  in  the 
larva  of  Ephemera.  The  arrows  indicate  the  current  of  the 
fluid. 

The  muscular  system  of  insects  is  very  extensive.  Lyonet 
dissected  and  described  4061  in  the  caterpillar  of  the  goat  moth 
(Cossus  liyniperdci). 

10* 


CHAPTER   IX. 


THE    CELL-DOCTRINE    OF    PHYSIOLOGY. 

• 

REFERENCE  has  already  been  made  at  page  96  to  the  cause 
of  vitality;  alluding  to  it  as  a  peculiar  property  impressed  by 
the  Creator  on  all  organized  structure, — a  property  altogether 
distinct  from  Volition  and  Sensation,  which  exclusively  belong 
to  animals,  and  which  point  out  the  existence  of  a  special  entity, 
or  being,  resident  in  the  organism,  but  whose  properties  can- 
not properly  be  referred  either  to  matter  or  its  organization. 

Respecting  the  essential  nature  of  the  vital  principle,  much 
speculation  has  been  uselessly  employed.  Some  have  con- 
founded it  with  the  entity,  or  being,  in  the  animal,  which 
perceives  and  wills.  But  this  is  manifestly  an  error,  inasmuch 
as  it  pertains  also  to  vegetables.  Very  many  parts  of  the 
organization,  also,  have  an  independent  vitality  (without 
special  sensibility),  separate  from  that  of  other  parts,  as  we 
shall  see  in  the  progress  of  this  chapter.  It  seems,  therefore, 
most  reasonable  to  define  it  as  a  peculiar  property  of  organi- 
zation; as  gravitation,  electricity,  &c.,  are  special  properties  of 
matter  under  other  circumstances,  the  essential  nature  of  which 
are  just  as  mysterious  as  that  of  Life. 

Mysterious  as  this  subject  is,  it  is  nevertheless  interesting  to 
trace  the  origin  and  development  of  organized  structures;  and 
the  progress  of  modern  science  has  supplied  us  with  the  means 


THE    CELL-DOCTRINE    OF    PHYSIOLOGY.         115 

of  instruction.  Chemistry  teaches  us  that  the  ultimate  ele- 
ments of  organized  bodies  are  identical  with  the  elements  of 
other  bodies ;  and  the  microscope  detects  the  earliest  forms 
produced  by  the  vital  process,  and  the  part  sustained  by  them 
in  the  development  of  each  species. 

Chemical  analysis  shows,  that  what  are  termed  simple  ele- 
ments, as  oxygen,  hydrogen,  carbon,  nitrogen,  sulphur,  &c., 
are  peculiarly  arranged  in  all  organized  bodies ;  having  special 
affinities  which  they  do  not  possess  in  unorganized  substances, 
or  bodies  destitute  of  life.  These  peculiar  affinities  form  a 
class  of  compound  substances  called  proximate  principles,  or 
organic  compounds,  or  organizable  substances.  They  are  ob- 
tained by  the  analysis  of  organized  textures  :  such  are  albumen, 
fibrin,  starch,  gluten,  &c. 

Owing  to  the  feeble  affinity  of  the  simple  elements  in  the 
organic  compounds,  there  is  a  great  tendency  in  them  to  enter 
into  new  combinations,  forming  what  are  called  secondary 
organic  compounds.  Such  are  urea,  uric  acid,  pepsine,  sugar 
of  milk,  &c. 

Hitherto,  no  one  has  succeeded  in  producing  the  true  proxi- 
mate principles  by  chemical  synthesis,  and  it  is  doubtful  if 
they  will  ever  be  produced  elsewhere  than  in  the  living  organism. 
Some  of  the  secondary  organic  compounds  have,  however,  been 
formed  in  the  laboratory  of  the  chemist ;  as  the  production  of 
urea  from  cyanate  of  ammonia  through  the  action  of  heat, 
which  has  been  effected  by  Wohler. 

"  The  simplest  and  most  elementary  organic  form  with  which 
we  are  acquainted,  is  that  of  a  cell,  containing  another  within 
it  (nucleus),  which  again  contains  a  granular  body  (nucleolus)." 
See  Fig.  32. 

"  This  appears,  from  the  interesting  researches  of  Schleiden 
and  Schwarm,  to  be  the  primary  form  which  organic  mat- 
ter takes  when  it  passes  from  the  condition  of  a  proximate 


116  THE     MICROSCOPIST. 

principle  to  that  of  an  organized  structure."   (  Todd  and  Bow- 
man.') 

There  are  some  animal  tissues,  however,  which  seem  to  have 
a  lower  grade  of  organization   than  cells,   being  apparently 


produced  by  the  simple  solidification  of  the  plastic  or  organi- 
zable  fluid  :  this  fluid  is,  however,  prepared  by  cells,  and  is  set 
free  by  their  rupture.  This  seems  to  be  the  case  with  the 
delicate  membrane  known  as  the  Basement  or  Primary  Mem- 
brane, beneath  the  epidermis  or  epithelium.  According  to 
Dr.  Carpenter,  in  many  specimens  of  this  membrane,  no  ves- 
tige of  cell-structure  can  be  seen,  and  it  resembles  that  of 
which  the  walls  of  the  cells  are  themselves  constituted.  In 
other  cases  it  presents  a  granular  appearance  under  the  micro- 
scope, and  is  then  supposed  by  Henle  to  consist  of  the  coalesced 
nuclei  of  cells,  whose  development  has  been  arrested.  Other 
specimens  of  basement  membrane,  however,  described  by 
Goodsir,  present  a  distinctly  cellular  structure,  the  cells  being 
polygonal,  and  each  having  its  own  granular  nucleus. 

Cells  are  formed  in  two  ways ;  either  in  a  previously  exist- 
ing, structureless  fluid  called  a  blastema,  or  within  the  interior 
of  previously  existing  cells.  In  the  first  method,  the  plastic 
fluid  becomes  opalescent  from  the  deposition  of  a  number  of 
nucleoli;  several  of  these  become  aggregated,  and  form  the 
nucleus,  within  which  the  nucleolus  can  still  be  seen.  This 
nucleus  is  called  the  cytoblast  (from  xurocr,  a  vesicle,  and  /3Xa£o£, 
a  germ),  or  cell-germ.  From  the  side  of  this  nucleus  a  thin 
transparent  membrane  projects  like  a  watch-crystal  from  the 


THE    CELL-DOCTRINE    OF    PHYSIOLOGY.         117 

dial,  and  gradually  enlarges  till  at  last  the  nucleus  is  seen  only 
as  a  spot  on  its  wall.  The  whole  is  then  called  a  nucleated 
cell,  or  germinal  cell  The  fluid  in  which  the  granules  are  first 
deposited  is  called  the  cytoUastema. 

In  the  second  method  of  development,  each  granule  of  the 
nucleus  has  the  power  of  developing  a  cell,  so  that  the  parent 
cell  becomes  filled  with  one  or  more  generations  of  new  cells, 
which  may  either  disappear  entirely,  or  by  the  rupture  of  the 
original  cells  the  contents  may  be  scattered  and  undergo  an 
independent  development. 

Sometimes  several  nucleoli  are  seen  within  one  nucleus,  and 
several  nuclei  within  one  cell. 

Each  cell  is  an  independent  organ,  living  for  itself,  and  by 
itself,  and  depending  upon  nothing  but  a  proper  supply  of  nu- 
triment and  of  the  appropriate  stimuli  for  the  continuance  of 
its  growth  and  for  the  performance  of  its  functions,  until  its 
term  of  life  is  expired. 

The  development  of  cells  goes  on  at  every  period  during  the 
life  of  the  organism.  They  are  found  floating  in  immense 
numbers  in  the  blood,  chyle,  and  lymph ;  and  even  in  dis- 
eased secretions,  as  pus.  In  the  inflammatory  process  they 
are  produced  in  great  quantities ;  and  the  malignant  growths, 
such  as  cancer  and  fungus  hsematodes,  which  infest  the  body, 
are  owing  to  the  same  agencies.  In  short,  the  nucleated  cell  is 
the  agent  of  most  of  the  organic  processes,  both  in  the  plant 
and  animal,  from  the  dawn  of  their  existence  to  their  full 
maturation  and  decline. 

The  forms  of  cells  are  various;  some  being  spheroidal,  others 
cubical,  prismatic,  polygonal,  or  cylindrical.  They  are  subject 
also  to  various  transformations.  Sometimes  a  number  of 
cylindrical  cells  are  laid  end  to  end,  and  by  the  absorption  of 
the  transverse  partitions  form  a  continuous  tube ;  as  in  the 
sap  vessels  of  plants,  muscular  and  nervous  fibre,  &c. 

At  other  times  the  cells  are  elongated  and  fusiform,  as  in 


118  THE    MICROSCOPIST. 

woody  fibre ;  or  they  may  send  forth  prolongations,  assuming 
a  stellate  or  irregular  appearance,  as  in  the  pigment  cells  of 
the  Batrachia  and  Fishes,  or  some  of  the  vesicles  in  the  gray 
matter  of  the  nervous  system.  Further,  the  original  bounda- 
ries of  the  cells  may  be  altogether  lost,  from  their  coalescence 
with  each  other;  or  their  cavities  be  so  occupied  by  internal 
deposits  that  they  may  be  mistaken  for  solid  fibres. 

The  nuclei  are  also  subject  to  change  of  form.  In  some 
instances  we  find  it  sending  out  radiating  prolongations,  so  that 
it  assumes  a  stellate  form,  like  that  of  the  cells  of  the  Grera- 

%  Fig.  33. 


nium-petal,  Fig.  33 ;  this  seems  also  to  be  the  case  with  the 
nuclei  of  the  bone  cells.  In  other  cases  it  seems  to  resolve 
itself  into  a  fasciculus  of  fibres ;  and  this  Henle  conceives  to  be 
the  origin  of  the  yellow  fibrous  tissue.  Further,  it  may  sepa- 
rate into  a  number  of  distinct  fibres,  each  composed  of  a  linear 
aggregation  of  granules ;  in  this  manner,  the  dental  tubuli 
appear  to  be  formed.  Lastly,  Dr.  Carpenter  thinks  it  may 
disperse  itself  still  more  completely  into  its  component  gra- 
nules y  by  the  reunion  of  which  certain  peculiar  vibrating  fila- 
ments (the  so-called  spermatozoa)  may  be  formed. 


THE    CELL-DOCTRINE    OF    PHYSIOLOGY.          119 

"  In  the  lowest  and  simplest  forms  of  living  beings/'  says 
Dr.  Carpenter,  "  such  as  we  meet  with  among  the  humblest 
cellular  plants,  we  find  a  single  cell  making  up  the  whole 
fabric.  This  cell  grows  from  its  germ,  absorbs  and  assimilates 
nutriment,  converts  a  part  of  this  into  the  substance  of  its 
own  cell-wall,  secretes  another  portion  into  its  cavity,  and 
produces  from  a  third  the  reproductive  germs  that  are  to 
continue  the  race ;  and  having  reached  its  own  term  of  life, 
and  completed  the  preparation  of  these  germs,  it  bursts  and 
sets  them  free — every  one  of  these  being  capable,  in  its  turn, 
of  going  through  the  same  set  of  operations.  In  the  highest 
forms  of  vegetable  life,  we  find  but  a  multiplication  of  similar 
cells;  amongst  which  these  operations  are  distributed,  as  it 
were,  by  a  division  of  labour;  so  that,  by  the  concurrent 
labours  of  all,  a  more  complete  and  permanent  effect  may  be 
produced." 

Of  the  development  of  animal  tissues,  Todd  and  Bowman 
present  the  following  interesting  account,  in  their  "  Physiolo- 
gical Anatomy  and  Physiology  of  Man." 

"  The  prevailing  mode,  in  which  the  development  of  animals 
takes  place,  is  by  the  formation,  within  the  parent,  of  a  body 
containing  the  rudiments  of  the  future  being,  as  well  as  a  store 
of  nutrient  material  sufficient  to  nourish  the  embryo  for  a 
longer  or  shorter  period.  This  body  is  called  the  ovum  or  egg. 
It  is  of  that  form  which,  in  a  former  page  (see  Fig.  32,  page 
116),  has  been  described  and  delineated  as  the  simplest  which 
organization  produces.  It  consists  of  a  vesicular  body  filled 
by  a  fluid,  and  enclosing  another,  within  which  is  a  third,  con- 
sisting of  one  or  more  minute,  but  clear  and  distinct  granules. 
The  first,  or  vitelline  membrane  of  the  ovum,  is  the  wall  of  a 
cell ;  it  is  composed  of  homogeneous  membrane :  the  second, 
or  the  germinal  vesicle  of  the  egg,  is  the  nucleus  of  the  first : 
and  the  third,  which  is  called  by  embryologists  the  germinal 


120  THE     MICROSCOPIST. 

spot,  is  a  nucleolus  to  the  second.  It  appears,  from  the  re- 
searches of  Wagner  and  Barry,  that  the  nucleus  or  germinal 
vesicle  precedes  the  formation  of  the  vitelline  membrane,  but 
the  precise  relation,  as  to  the  period  of  its  formation,  of  the 
nucleolus  or  germinal  spot  to  the  nucleus,  has  not  yet  been 
satisfactorily  made  out.  The  germinal  vesicle  and  spot  become 
the  seat  of  a  series  of  changes,  which  give  rise  to  the  develop- 
ment of  new  cells,  for  the  formation  of  the  embryo. 

"At  this  period  the  embryo  consists  of  an  aggregate  of  cells, 
and  its  further  growth  takes  place  by  the  development  of  new 
ones.  This  may  be  accomplished  in  two  ways :  first,  by  the 
development  of  new  cells  within  the  old,  through  the  subdivi- 
sion of  the  nucleus  into  two  or  more  segments,  and  the  forma- 
tion of  a  cell  around  each,  which  then  becomes  the  nucleus  of 
a  new  cell,  and  may  in  its  turn  be  the  parent  of  other  nuclei : 
and,  secondly,  by  the  formation  of  a  granular  deposit  between 
the  cells,  in  which  the  development  of  the  new  cells  takes 
place.  The  granules  cohere  to  each  other  in  separate  groups 
here  and  there,  to  form  nuclei,  and  around  each  of  these  a 
delicate  membrane  is  formed,  which  is  the  cell-membrane. 

"  In  every  part  of  the  embryo  the  formation  of  nuclei  and 
of  cells  goes  on  in  one  or  both  of  the  ways  above  mentioned; 
and,  by  and  by,  ulterior  changes  take  place,  for  the  production 
of  the  elementary  parts  of  the  tissues." 

The  mode  of  development  just  referred  to  maybe  illustrated 
by  the  following  cuts.  Fig.  34  exhibits  a  section  of  one  of 
the  branchial  cartilages  of  the  young  tadpole.  Within  the 
large  parent-cells,  that  are  held  together  by  intercellular  sub- 
stance, a,  6,  c,  we  observe  secondary  cells  in  various  stages  of 
development :  at  d,  the  nucleus  is  single ;  at  e,  it  is  dividing 
into  two;  in  the  adjoining  cell,  the  division  into  two  nuclei, 
d'  and  e',  is  complete ;  at  A,  two  such  nuclei  are  enclosed  within 
a  common  cell-membrane ;  at  i,  we  see  three  new  cells  (one  of 


THE    CELL-DOCTRINE    OF    PHYSIOLOGY.         121 

them  elongated,  and  probably  about  to  subdivide)  within  the 
parent ;  and  in  each  of  the  two  groups  at  the  top  and  bottom 

Fig.  34. 


of  the  figure,  we  have  four  cells,  separated  by  partitions  of  in- 
tercellular substance,  but  having  manifestly  originated  from 
one  parent  cell. 

Fig.  35  represents  endogenous  cell-growth  in  cells  of  a  rne- 
liceritous  tumour;  a,  cells  presenting  nuclei  in  various  stages 
of  development  into  a  new  generation ;  6,  parent-cell  filled 
with  a  new  generation  of  young  cells,  which  have  originated 
from  the  granules  of  the  nucleus. 

The  following  arrangement  of  animal  tissues  is  based  upon 
that  adopted  by  Dr.  Carpenter. 

1.  Simple  membrane;  homogeneous,  or  nearly  so,  employed 
alone,  or  in  the  formation  of  compound  membranes.  Its 
principal  character  is  extension,  but  its  ultimate  structure  de- 
fies the  highest  powers  of  the  microscope. — Examples  are  seen 
in  the  posterior  layer  of  the  cornea,  capsule  of  the  lens,  sar- 
colemma  of  muscle,  &c. 

11 


122 


THE    MICROSCOPIST. 


2.  Simple  fibrous  tissues,  including  the  white  and  yellow 
fibrous  tissue,  and  the  areolar  tissue,  which  is  formed  from 

Fig.  35. 


them.     Henle  believes  the  white  fibrous  tissue  to  be  formed 
by  cells;  the  yejlow,  by  nuclei. 

3.  Simple  cells,  floating  separately  and  freely  in  the  fluids, 
as  corpuscles  of  the  blood,  lymph,  and  chyle. 

4.  Simple  cells  developed  on  the  free  surfaces  of  the  body, 
as  epidermis  and  epithelium. 

5.  Compound  membranes ;  composed  of  simple  membrane, 
and  a  layer  of  cells,  of  various  forms  (epithelium  and  epi- 
dermis) ;  or  of  areolar  tissue  and  epithelium  j  as  mucous  mem- 
brane, skin,  secreting  glands,  serous  and  synovial  membranes. 

6.  Simple  isolated   cells,   forming   solid   tissues   by    their 
aggregation ;  as  fat  cells,  the  vesicles  of  gray  nervous  matter, 


THE    CELL-DOCTRINE    OP    PHYSIOLOGY.         123 

absorbent  cells  of  the  villi,  and  the  cellular  parenchyma  of  the 
spleen.  In  these  cases  the  cells  are  held  together  by  the  blood- 
vessels and  areolar  tissue,  which  pass  in  between  them;  in 
cartilage,  and  other  tissues  allied  to  it  in  structure,  the  cells  are 
united  by  intercellular  substance,  either  homogeneous,  or  of  a 
fibrous  character. 

7.  Sclerous  or  hard  tissues,  in  which  the  cells  have  been 
more  or  less  consolidated  by  internal  deposit,  and  more  or  less 
completely  coalesced  with  each  other;  as  the  hair,  nails,  &c. 
These  instances  may  be  more  properly  ranked  under  the  epi- 
dermic  tissues;   the   result  of  consolidated   deposit  is  more 
characteristically  seen  in  bones  and  teeth. 

8.  Tubular  tissues ;  formed  by  the  coalescence  of  the  cavi- 
ties of  cells ;  as  in  the  capillary  blood-vessels,  muscular  fibre, 
tubuli  of  nerves,  &c. 

In  some  of  these,  as  muscle  and  nerve,  a  deposit  has  taken 
place  subsequently  to  the  coalescence  of  the  original  cells. 

To  these  we  may  add, — 9.  Compound  tissue ;  formed  of 
areolar  tissue  and  cartilage;  as  fibro-cartilage. 


CHAPTER    X. 

EXAMINATION    OP    MORBID    STRUCTURES,    ETC. 

FOR  the  purpose  of  making  a  microscopic  analysis  of  ab- 
normal or  other  fluids,  certain  chemicals  will  be  required ;  as 
liquor  potassse,  ammonia,  ether,  and  alcohol,  acetic,  nitric, 
hydrochloric  and  sulphuric  acids;  together  with  a  few  test- 
tubes  and  watch-glasses. 

In  the  case  of  solids,  the  various  kinds  of  scalpels,  dissect- 
ing needles,  and  Valentin's  knife,  will  be  useful. 

If  the  subject  for  examination  be  fluid,  as  blood,  pus,  mu- 
cus, &c.,  a  very  small  quantity  should  be  put  on  a  clean  slide, 
and  covered  with  a  piece  of  thin  glass.  A  fishing-tube  (page 
47)  will  be  of  service  for  this  purpose. 

If  there  be  sediment  in  the  fluid,  it  should  be  allowed  to  sub- 
side, when  it  can  be  transferred  by  the  fishing-tube  to  the 
slide.  A  small  quantity  of  any  reagent  which  may  be  de- 
sired, may  be  brought  in  contact  with  one  of  the  sides  of  the 
thin  glass  cover,  when  it  will  gradually  insinuate  itself  between 
the  glasses,  and  act  slowly  on  what  is  contained  there.  In 
other  cases,  the  cover  may  be  lifted  up,  and  the  reagent 
added. 

In  the  case  of  blood,  the  fluids  that  require  to  be  added  are 
generally  ordinary  water ;  serum ;  and  sugar  or  salt,  dissolved 
in  water;  but  in  the  case  of  pus  and  mucus,  which  approach 


MORBID     STRUCTURES,     ETC.  125 

each  other  so  nearly  in  many  of  their  characters,  it  becomes 
of  importance  to  have  some  test  whereby  they  may  be  dis- 
tinguished from  each  other.  The  fluid  employed  for  this 
purpose  is  acetic  acid.  When  this  is  added  to  a  fluid  where 
pus  is  present,  the  globules  swell  up,  and  several  large,  trans- 
parent nuclei  make  their  appearance ;  but  when  it  is  added  to 
a  fluid  where  mucus  is  present,  the  globules  also  enlarge  and 
show  their  nuclei,  but  not  so  plainly  as  the  pus,  and  the  liquid, 
termed  liquor  muci,  in  which  the  globules  float,  is  instantly 
coagulated  into  a  semi-opaque  corrugated  membrane. 

The  presence  of  fatty  matter  is  ascertained  by  sulphuric 
ether,  which  readily  dissolves  the  oily  part,  and  leaves  the 
membranous  cell-wall  untouched. 

Earthy  matters  require  the  aid  of  the  acids  for  their  solu- 
tion ;  these  should  be  added  in  a  dilute  form,  so  that  their 
solvent  action  may  be  more  easily  witnessed. 

Solid  parts,  as  tumours,  &c.,  that  are  to  be  examined  as 
transparent  objects,  with  high  powers,  require  to  be  cut  into 
very  thin  slices,  and  separated,  if  necessary,  by  the  needle- 
points. The  sections  should  be  placed  on  a  slide,  and  a  little 
serum,  or  white  of  egg  in  water,  added,  in  order  to  float  out 
certain  of  the  parts,  and  to  lessen  the  refraction  of  the  light 
at  the  edges  of  the  object.  Water  will  answer  the  purpose 
for  some  of  the  hard  tissues,  but  where  nucleated  or  other 
cells,  and  nervous  matter,  are  present,  its  use  is  inadmissible. 

It  is  necessary  to  state,  that  the  examination  of  all  morbid 
structures  should  be  made  as  soon  as  convenient  after  their 
removal  from  the  body,  as  changes  of  form  in  the  softer  sub- 
stances speedily  take  place;  but  if  some  time  has  elapsed, 
the  part  from  which  the  sections  are  taken  should  be  at  some 
distance  from  the  surface,  in  order  that  they  may  be  as  little 
altered  as  possible  by  the  action  of  the  air. 

The  foregoing  directions  have  been  condensed  from  those  of 
11* 


126  THE    MICROSCOPIST. 

Mr.  Quekett,  to  whose  book  we  have  already  been  much  in- 
debted during  the  progress  of  this  work. 

It  was  at  one  time  "  fondly  hoped"  (says  Dr.  McClellan), 
"  that  by  the  aid  of  powerful  microscopes  we  could  be  able  to 
detect  the  pre-existing  germs  of  all  organic  diseases  in  the 
general  circulation,  and  decide  not  only  as  to  the  species  of 
affection,  but  also  concerning  the  degree  of  constitutional  con- 
tamination. It  was  even  thought  that  cancers  could  thus  be 
distinguished  from  scrofula  and  all  other  more  innocent  dis- 
eases; while,  at  the  same  time,  we  could  form  a  conclusive 
opinion  as  to  the  propriety  of  attempting  or  declining  a  sur- 
gical operation,  or  of  instituting  any  mode  of  local  treatment 
for  the  purpose  of  affording  relief.  But  all  such  attempts 
have  proved  to  be  illusory,  and  we  can  gather  no  other  practi- 
cal knowledge  from  the  use  of  the  microscope  than  what  is 
connected  with  the  minute  anatomy  of  the  morbid  structures 
after  they  have  been  elaborated."  With  all  deference  to  the 
opinion  of  so  truly  a  great  mind  as  the  lamented  McClellan, 
we  may  be  permitted  to  remark,  that  notwithstanding  much 
has  been  done  by  the  labours  of  European  and  other  observers, 
minute  pathological  observation  is  still  in  its  infancy;  yet  it 
has  made  a  deep  impression  upon  the  study  of  medical  science. 
When  "the  minute  anatomy  of  the  morbid  structures"  shall 
be  fully  known,  our  knowledge  of  organic  diseases  will  have 
advanced  to  a  great  degree  of  perfection.  Dr.  McClellan  is 
not  himself  insensible  of  the  advantages  to  be  derived  from 
microscopic  investigations,  although  we  think  he  places  too 
little  value  upon  them.  He  says,  "  Chemical  analyses  and 
microscopic  researches  have  lately  proved  that  a  great  number 
of  cases  (of  tumours)  which  were  once  thought  to  be  scirrhous, 
or  cartilaginous,  or  osteo-sarcomatous,  are  really  composed  of 
condensed  fibrine  of  the  blood,  sometimes  partially  altered  into 
albumen  or  gelatin." 


MORBID     STRUCTURES,    ETC.  127 

The  microscopic  appearance  of  a  fibrous  tumour  is  exhibited 
in  Fig.  36  (after  Vogel).     It  shows  interlacing  fibres,  C.    Pri- 


Fig.  36. 


mary  cells  with  nuclei  and  nucleoli,  A,  and  the  same  cells 
elongated  and  becoming  caudate,  B.  The  interlacing  fibres 
appear  to  be  identical  with  the  fibres  of  coagulated  lymph. 

Malignant  growths  may  be  divided  into  three  classes  of 
disease.  1.  Scrofula,  and  its  varieties.  2.  Carcinoma,  or 
scirrho-cancer.  3.  Encephaloid  disease,  or  medullary  fungus. 

1.  Scrofulous  growths  present  three  forms  of  manifestation. 
In  the  lymphatic  ganglia  and  in  the  conglomerate  glands ;  in 
well-defined  spherical  tubercles,  which  appear  first  as  small 
points  or  grayish  granules  ]  and  depositions  which  appear 
during  the  progress  of  typhus  fever,  between  the  muscular 
and  mucous  coats  of  the  intestines,  in  the  mesenteric  glands, 
in  and  under  the  mucous  membrane  of  the  trachea,  and  some- 
times in  the  substance  of  the  lungs  and  spleen.  Fig.  37  shows 
the  microscopic  appearance  of  typhous  matter  from  the  mesen- 
teric glands.  A,  an  amorphous,  slightly  granular  mass,  of  a 


128  THE    MICROSCOPIST. 

brownish-white  colour,  with  an  immense  number  of  cells  depo- 
sited; B,  the  amorphous  mass  treated  with  acetic  acid,  by 
which  it  was  rendered  transparent,  and  gradually  dissolved, 

Fig.  37. 


upon  which  many  minute  cells  with  a  sharp  outline  came  into 
view,  being  unaffected  by  the  acid  (Vogel). 

There  seems  no  distinction  between  tuberculous  matter  and 
that  of  scrofula  or  typhus.  Fig.  38  exhibits  tubercles  in 
various  stages  of  development.  A,  B,  C,  tubercles  from  the 
lungs  of  a  young  man  who  died  of  tuberculosis  pulmonum. 

A,  B,  nuclei  in  an  amorphous  cytoblastema ;  most  of  the 
nuclei  contain  nucleoli.  At  C  the  cytoblastema  has  disap- 
peared and  the  cells  are  in  contact.  D,  tubercular  cells  from 
the  lungs  of  another  young  man.  Here  the  cytoblastema  has 
also  disappeared,  and  the  nuclei  are  enclosed  in  a  cell-wall ;  no 
nucleoli  are  present. 


MORBID     STRUCTURES,    ETC. 


129 


2.  Carcinoma.  In  cases  of  true  scirrhus,  the  matrix  or 
stroma  is  constituted  either  by  a  new  development  of  cellular 
texture,  or  by  an  induration  and  enlargement  of  the  original 
areolar  tissue  of  the  part.  The  larger  and  coarser  fibres  and 

lig.  38. 


lamellae  of  this  tissue  become  converted  into  dense  and  firm 
ligamentous  bands,  which  intersect  each  other  in  various 
directions. 

Vogel,  and  some  other  writers,  describe  a  second  kind  of 
fibres,  which  occur  in  a  reticulated  form,  cross-barred,  or  in 
irregular  meshes.  They  are  distinguished  from  the  first-men- 
tioned whitish  or  ligamentous  bands,  by  being  insoluble  in 
acetic  acid.  Fig.  39  (from  Vogel,  after  Mu'ller),  shows  the 

Fig.  39. 


fibrous  stroma  of  scirrhus,  as  seen  in  the  microscope.     The 


130  THE     MICROSCOPIST. 

ineshes  are  formed  by  bundles  of  carcinoma  reticulare  of  the 
breast,  as  they  appear  after  the  globules  have  been  removed. 

The  dense,  firm,  bluish-white,  or  yellowish  and  amorphous- 
looking  substance  which  fills  the  interstices  of  the  stroma  is 
rendered  transparent  by  acetic  acid,  and  by  ammonia  and  other 
caustic  alkalies.  This,  though  deposited  in  a  fluid  state,  ac- 
quires its  solidity  by  coagulation,  after  which  it  is  thought 
that  the  peculiar  cancer  cells,  or  fibres,  which  constitute  the 
malignant  character  of  the  disease,  are  developed. 

The  principal  forms  of  cells  which  enter  into  the  composi- 
tion of  cancerous  growths  are — 1.  The  irregularly  caudate  or 
ramifying  cells;  2.  Larger  cells  filled  with  nuclei;  and  3. 
Granular  cells  filled  and  covered  with  granules.  Besides  these 
Vogel  describes  cells  with  a  thick  wall,  exhibiting  a  double 
contour;  double  cells  formed  by  the  division  of  one  or  the 
fusion  of  two  cells;  and  pigment  cells,  enclosing  dark,  granular 
pigment. 

The  above  are  transitory  or  effete  cells.  The  persistent  or 
fibre  cells  are  fusiform,  such  as  occur  in  the  development  of 
areolar  tissue,  and  of  simple  muscular  fibre.  They  occur  in 
the  firm,  rarely  in  the  soft  forms  of  cancer,  and  seem  destined 
for  the  formation  of  the  areolar  tissue,  and  the  intersecting 
ligamentous  bands.  In  addition  to  all  these,  there  appear 
numerous  particles  or  granules  of  broken-down  lymph  and  fat ; 
large  fat  granules  and  globules;  and  a  viscid,  gelatinous  fluid. 
These  latter,  however,  may  be  considered  adventitious  and  not 
essential  formations. 

The  microscopic  appearance  of  scirrhus  (220  diameters)  is 
exhibited  in  Fig.  40.  Small  masses  that  had  been  pared  from 
a  recent  section  of  the  tumour,  and  moistened  in  water,  con- 
sisted entirely  of  an  accumulation  of  cells.  These  were  very 
pale,  varying  in  size  and  form,  being  sometimes  roundish,  a, 
sometimes  oval,  b,  or  caudate,/,  or  again  of  irregular  form. 


MORBID     STRUCTURES,     ETC. 


131 


The  greater  number  exhibited  nuclei,  a,  6,  and  in  some  a  nu- 
cleolus  was  visible  in  the  nucleus,  c,  h;  few  were  devoid  of 


lig.  40. 


nuclei;  on  some  fat  globules  were  observed,  g.  Between 
these  cells  were  perceived  nuclei  with  or  without  nucleoli,  d. 
(Vogel.) 

3.  Encephaloid  disease  or  fungoid  tumour,  differs  from 
scirrhous  cancer  chiefly  in  the  great  predominance  of  its  transi- 
tory or  morbidly  developed  cells  over  the  fibrous  and  other 
elementary  textures  which  constitute  the  stroma  (matrix)  of 
the  tumour.  In  carcinomas,  the  fibrous  tissue  predominates 
and  gives  solidity  and  firmness  to  the  whole  mass.  The  morbid 
or  cancer  cells  never  tend  to  develope  organized  fabrics,  but 
always  to  disintegration  and  softening  down  of  the  tumour. 
Their  great  predominance  in  encephaloid,  therefore,  gives  the 
character  of  brain-like  softness  and  yielding,  which  is  the  dis- 
tinguishing characteristic  of  this  form  of  malignant  growth. 

Fig.  41  represents  encephaloid,  from  the  liver,  under  the 
microscope.  It  appeared  wholly  composed  of  cells,  which 
showed  distinct  nuclei  and  nucleoli.  The  cells  were  mostly 
roundish  or  oval,  but  some  were  caudate.  Acetic  acid  ren- 
dered them  full  and  brought  the  nuclei  plainly  in  view,  a. 


132  THE    MICROSCOPIST. 

Here  and  there  some  nuclei  were  seen  in  an  amorphous  cyto- 
blastema. 


Fig.  41. 


Although  the  cells  of  encephaloid  belong  to  the  class  of 
effete  or  transitory  cells  which  also  occur  in  cancer,  yet  there 
is  a  difference  in  the  proportions  of  various  kinds  of  these  cells 
in  the  two  classes  of  tumours.  The  predominating  cells  of  this 
kind  in  fungoid  tumour  are  the  very  large  parent  cells,  with 
numerous  young  cells  or  cytoblasts  in  their  interior.  They  are 
often  as  large  as  ^th  of  a  line  in  diameter ;  and  the  caudate 
cells  are  always  irregularly  caudate  or  ramifying. 

There  are  seldom  any  of  the  regular  caudate  or  elongated 
cells  of  small  size,  such  as  go  to  the  formation  of  the  cellular 
and  fibrous  tissue,  and  of  true  cancers.  The  fat  cells  and 
granules  are  perhaps  more  abundant  than  in  scirrhus.  Fig. 
42  is  the  microscopic  appearance  of  encephaloid,  consisting  of 
cells  of  different  size  and  form  ;  round,  oval,  and  caudate,  but 
no  one  form  predominating  over  the  rest.  Some  are  very  large, 
a,  enclosing  several  minute  cells  with  nuclei.  Isolated  cells, 
although  in  a  proportionately  small  number,  contained  dark 
granules,  b.  For  further  observations  on  microscopic  patho- 


MORBID    STRUCTURES,    ETC.  133 

logy,  the  reader  is  referred  to  YogeFs  Pathological  Anatomy, 
and  other  similar  works. 

Fig.  42. 


The  Monthly  Journal  of  Medical  Science  for  May,  1847, 
contained  an  account  of  a  new  instrument  for  the  diagnosis  of 
tumours.  It  was  presented  to  the  Medical  Society  of  Stras- 
bourg, by  M.  Kiin,  Professor  of  Physiology  in  that  city. 

"It  consists  in  an  exploring  needle,  having  at  its  extremity 
a  small  depression  with  cutting  edges.  On  plunging  this  in- 
strument into  a  tumour  to  any  depth,  we  can  extract  a  minute 
portion  of  the  tissue  of  which  its  various  layers  are  composed. 
In  this  manner  a  microscopic  examination  of  the  tumour  can 
be  practised  on  the  living  subject,  and  its  nature  ascertained 
before  having  recourse  to  an  operation." 

With  respect  to  the  Morphology  of  various  pathological 
fluids,  a  great  deal  has  been  effected  by  microscopic  investiga- 
tion. In  the  Microscopic  Journal,  vol.  ii.,  is  a  series  of  essays 
on  this  subject,  by  Dr.  David  Gruby,  translated  from  the 
Latin  by  S.  J.  Groodfellow,  M.D.,  which  are  worthy  of  careful 
perusal  and  experimental  verification.  The  results  of  Dr. 
G-ruby's  researches  may  be  found  in  a  tabular  form  at  the  end 
of  this  volume. 

12 


CHAPTER  XL 


ON    MINUTE    INJECTIONS. 

MERE  dissection,  with  the  most  artful  management  of  the 
scalpel,  cannot  make  a  full  exhibition  of  the  true  structure 
of  animal  bodies.  The  arteries  are  found,  after  death,  to  be 
emptied  of  their  contents,  and  the  blood  is  coagulated  in  the 
veins,  which  appear  much  collapsed;  hence  anatomists,  in 
order  to  examine  the  circulatory  apparatus,  are  under  the 
necessity  of  filling  these  vessels  by  means  of  injection,  in 
order  to  distend  them  as  much  as  possible,  that  their  ramifica- 
tions may  be  clearly  seen.  More  especially  is  this  necessary 
when  it  is  desired  to  make  an  exhibition  of  the  minute 
capillaries,  which  are  so  variously  arranged  in  the  different 
textures  and  organs  of  the  body.  These  small  vessels,  too, 
require  the  aid  of  the  microscope  to  show  their  size,  form,  and 
arrangement. 

The  ordinary  coarse  injection,  may  be  made  by  melting  to- 
gether 16  ounces  of  bees' -wax,  8  ounces  of  resin,  and  6  fluid- 
ounces  of  turpentine  varnish,  adding  such  colouring  matter  as 
may  be  desirable,  as  3  ounces  vermilion,  2  ounces  King's 
yellow,  10  ounces  blue  verditer,  or  5£  ounces  flake-white. 

This,  injected  into  the  blood-vessels  by  a  proper  syringe, 
having  its  pipe  fastened  in  one  of  the  largest  of  those  vessels, 
is  abundantly  sufficient  to  show  the  course  of  the  principal 
arteries  and  veins.  The  parts  so  injected  may  then  be  dis- 


ON    MINUTE    INJECTIONS.  135 

sected  for  this  purpose,  dried,  and  varnished,  and  form  excellent 
illustrations  of  anatomical  lectures. 

When,  however,  it  is  desired  to  demonstrate  the  capillaries, 
a  finer  injection  and  more  delicate  manipulation  is  required. 
Indeed,  it  is  so  difficult  an  art,  and  success  is  so  dependent  on 
the  combination  of  various  circumstances,  that  the  most  ex- 
perienced are  often  defeated  in  their  efforts.  Yet  some  of  the 
finest  injections  I  have  ever  seen  were  made  by  those  who 
attempted  it  for  the  first  time. 

For  minute  injection  (as  it  is  called),  the  most  essential  in- 
strument is  a  proper  syringe.  This  should  be  made  of  brass, 
of  such  a  size  that  the  tip  of  the  thumb  may  press  on  the 
head  or  handle  of  the  piston-rod  when  drawn  out,  while  the 
body  is  supported  by  two  of  the  fingers  of  the  same  hand. 

Fig.  43  represents  a  syringe,  with  which  I  have  succeeded 
in  making  some  excellent  preparations.  A  is  the  cylindrical 
brass  body,  on  the  top  of  which  screws  the  cap,  B,  a  leather 
washer  being  interposed  to  render  it  more  air-tight.  C  is  the 
piston,  which  is  of  brass,  covered  with  wash-leather.  The 
bottom  of  the  syringe,  D,  also  unscrews,  for  convenience  of 
cleaning.  E  is  a  stop-cock,  on  the  end  of  which  another  stop- 
cock, F,  fits  closely.  On  the  end  of  this,  one  of  the  injection- 
pipes,  Gr,  which  are  of  different  sizes,  may  be  placed.  The 
transverse  wires,  across  the  injection-pipes,  are  designed  for 
the  better  security  of  the  pipe  in  the  vessel  into  which  it  is 
fixed ;  the  thread  being  tied  behind  them  so  that  it  cannot  slip 
forwards.  A  half-dozen  pipes,  at  least,  are  necessary  to  ac- 
company each  instrument. 

In  addition  to  the  syringe,  a  large  tin  vessel  to  contain  hot 
water,  with  two  or  three  lesser  ones  fixed  in  it  for  the  injec- 
tions, will  be  found  useful. 

To  prepare  the  material  for  injecting : — Take  of  the  finest 


136 


THE     MICROSCOPIST. 


and  most  transparent  glue,  one  pound;  break  it  into  small 
pieces,  put  it  into  an  earthen  pot,  and  pour  on  it  three  pints 
of  cold  water ;  let  it  stand  twenty-four  hours,  stirring  it  now 


Fig.  43. 


and  then  with  a  stick ;  then  set  it  over  a  slow  fire  for  half  an 
hour,  or  until  all  the  pieces  are  perfectly  dissolved ;  skim  off 


ON     MINUTE    INJECTIONS.  137 

the  froth  from  the  surface,  and  strain  through  a  flannel  for 
use.  Isinglass,  and  cuttings  of  parchment  make  an  excellent 
size,  and  are  preferable  for  very  particular  injections. 

The  size  thus  prepared  may  be  coloured  with  any  of  the 
following : 

Red. — To  1  pint  of  size,  2  ounces  of  Chinese  vermilion. 

Yellow. — Size,  1  pint, — chrome  yellow,  2  £  ounces. 

White. — Size,  1  pint, — flake-white,  3£  ounces. 

Blue.- — Size,  1  pint, — fine  blue  smalts,  6  ounces. 

It  is  necessary  to  remember  that  whatever  colouring  matter 
is  employed,  must  be  very  finely  levigated  before  it  is  mixed 
with  the  injection.  This  is  a  matter  of  great  importance,  for 
a  small  lump  or  mass  of  colour,  dirt,  &c.,  will  clog  the  minute 
vessels,  so  that  the  injection  will  not  pass  into  them,  and  the 
object  will  be  defeated. 

The  mixture  of  size  and  colour  should  be  frequently  stirred, 
or  the  colouring  matter  will  sink  to  the  bottom. 

Respecting  the  choice  of  a  proper  subject  for  injecting,  it 
may  be  remarked,  that  the  injection  will  usually  go  farthest 
in  young  subjects;  and  the  more  the  creature's  fluids  have 
been  exhausted  in  life,  the  greater  will  be  the  success  of  the 
injection. 

To  prepare  the  subject,  the  principal  points  to  be  aimed  at 
are,  to  dissolve  the  fluids,  empty  the  vessels  of  them,  relax  the 
solids,  and  prevent  the  injection  from  coagulating  too  soon. 
For  this  purpose  it  is  necessary  to  place  the  animal,  or  part  to 
be  injected,  in  warm  water,  as  hot  as  the  operator's  hand  will 
bear.  This  should  be  kept  at  nearly  the  same  temperature  for 
some  time  by  occasionally  adding  hot  water.  The  length  of 
time  required  is  in  proportion  to  the  size  of  the  part,  and  the 
amount  of  its  rigidity.  Ruysch  (from  whom  the  art  of  inject- 
ing has  been  called  the  Ruyschian  art,)  recommends  a  previous 
maceration  for  a  day  or  two  in  cold  water. 

12* 


138  THE    MIOROSCOPIST. 

When  the  size  and  the  subject  have  both  been  properly  pre- 
pared, have  the  injection  as  hot  as  the  finger  can  well  bear. 
One  of  the  pipes,  G-,  Fig.  43,  must  then  be  placed  in  the 
largest  artery  of  the  part,  and  securely  tied.  Put  the  stop- 
cock, F,  into  the  open  end  of  the  pipe,  and  it  is  then  ready  to 
receive  the  injection  from  successive  applications  of  the  syringe, 
A.  The  injection  should  be  thrown  in  by  a  very  steady  and 
gentle  pressure  on  the  end  of  the  piston-rod.  The  resistance 
of  the  vessels,  when  nearly  full,  is  often  considerable,  but  it 
must  not  be  overcome  by  violent  pressure  with  the  syringe. 
When  as  much  injection  is  passed  as  may  be  thought  advisa- 
ble, the  preparation  may  be  left  (with  the  stop-cock  closed  in 
the  pipe)  for  twenty-four  hours,  when  more  material  may  be 
thrown  in. 

As  the  method  of  injecting  the  minute  capillaries  with 
coloured  size  is  often  attended  with  doubtful  success,  various 
other  plans  have  been  proposed.  Ruysch's  method,  according 
to  Rigerius,  was  to  employ  melted  tallow,  coloured  with  ver- 
milion, to  which,  in  the  summer,  a  little  white  wax  was 
added. 

Mr.  Rauby's  material,  as  published  by  Dr.  Hales,  was  resin 
and  tallow,  of  each  two  ounces,  melted  and  strained  through 
linen ;  to  which  was  added  three  ounces  of  vermilion,  or  finely 
ground  indigo,  which  was  first  well  rubbed  with  eight  ounces 
of  turpentine  varnish. 

Dr.  Monro  recommended  coloured  oil  of  turpentine  for  the 
small  vessels,  after  the  use  of  which  he  threw  in  the  common 
coarse  injection. 

Professor  Breschet  frequently  employed  with  success  milk, 
isinglass,  the  alcoholic  solution  of  gum-lac,  spirit  varnish,  and 
spirit  of  turpentine ;  but  he  highly  commends  the  colouring 
matter  extracted  from  campeachy,  fernambone,  or  sandal 
woods.  He  says,  "  The  colouring  matter  of  campeachy  wood 


ON    MINUTE    INJECTIONS.  139 

easily  dissolves  in  water  and  in  alcohol;  it  is  so  penetrating 
that  it  becomes  rapidly  spread  through  the  vascular  networks. 
The  sole  inconvenience  of  this  kind  of  injection  is,  that  it  can- 
not be  made  to  distend  any  except  most  delicate  vessels,  and  that 
its  ready  penetration  does  not  admit  of  distinguishing  between 
arteries,  veins,  and  lymphatics."  He  also  recommends  a  solu- 
tion of  caoutchouc. 

Another  process,  which  may  be  termed  the  chemical  pro- 
cess, was  published  in  the  Comptes  Rendus,  1841,  as  the 
invention  of  M.  Doyere.  According  to  this,  an  aqueous  solu- 
tion of  bichromate  of  potass  is  propelled  into  the  vessels;  and 
after  a  short  time,  in  the  same  manner  and  into  the  same  ves- 
sels an  aqueous  solution  of  acetate  of  lead  is  injected.  This  is 
an  excellent  method,  as  the  material  is  quite  fluid,  and  the 
precipitation  of  the  chromate  of  lead,  which  takes  place  in 
the  vessels  themselves,  gives  a  fine  sulphur-yellow  colour. 

Dr.  Groadby  has  improved  upon  the  process  last  named  by 
uniting  to  the  chemical  solutions  a  portion  of  gelatine.  The 
following  is  his  formula,  originally  published  in  the  London 
Lancet,  and  again  in  the  Medical  Examiner,  March,  1850. 

Saturated  solution  of  bichromate  of  potash,  8  fluid  ounces ; 
water,  8  ounces;  gelatine,  2  ounces. 

Saturated  solution  of  acetate  of  lead,  8  fluid  ounces;  water, 
8  ounces;  gelatine,  2  ounces. 

Dr.  G-.  gives  the  following  remarks  respecting  this  process : 
— "The  majority  of  preparations,  thus  injected,  require  to  be 
dried,  and  mounted  in  Canada  balsam.  Each  preparation, 
when  placed  on  a  slip  of  glass,  will  necessarily  possess  more 
or  less  of  the  coloured  infiltrated  gelatine,  (by  which,  he 
alludes  to  the  gelatine,  coloured  by  the  blood,  which,  together 
with  the  acetate  of  potash  resulting  from  the  chemical  decom- 
position, may  have  transuded  through  the  coats  of  the  vessel,) 
which,  when  dry,  forms,  together  with  the  different  shades  of 


140  THE    MICROSCOPIST. 

the  chromate  of  lead,  beautiful  objects,  possessing  depth  and 
richness  of  colour.  The  gelatine  also  separates  and  defines 
the  different  layers  of  vessels.  By  this  injection  the  arteries 
are  always  readily  distinguishable  by  the  purity  and  brightness 
of  the  chromate  of  lead  within  them,  while  the  veins  are  de- 
tected by  the  altered  colour  imparted  by  the  blood. 

"Those  preparations  which  require  to  be  kept  wet,  can  be 
preserved  perfectly  in  my  B  fluid — specific  gravity  1-100; 
the  A  fluid  destroys  them. 

"I  would  recommend,  that  the  slips  of  glass  employed  for. 
the  dry  preparation  be  instantly  inscribed  with  the  name  of 
the  preparation,  written  with  a  diamond,  for,  when  dry,  it  is 
very  difficult  to  recognise  one  preparation  from  another,  until 
the  operator's  eye  be  educated  to  the  effects  of  this  chemico- 
gelatinous  injection.  Where  so  much  wet  abounds  gummed 
paper  is  apt  to  come  off. 

"  When  dry,  it  is  sufficient  for  the  purpose  of  brief  exami- 
nation by  the  microscope,  to  wet  the  surface  of  a  preparation 
with  clean  oil  of  turpentine ;  immediately  after  examination, 
it  should  be  put  away  carefully  in  a  box,  to  keep  it  from  the 
dust,  until  it  can  be  mounted  in  Canada  balsam. 

"  The  bichromate  of  potash  is  greatly  superior  in  colour  to 
the  chromate,  which  yields  too  pale  a  yellow;  and  subsequent 
experience  has  convinced  me  that  the  acetate  of  potash  fre- 
quently effects  its  liberation  by  destruction  of  the  capillaries, 
and  this,  even  long  after  the  preparations  have  been  mounted 
in  Canada  balsam;  perhaps  this  may  be  owing  to  some  chemical 
action  of  the  acetate  of  potash  upon  them. 

"  I  would  suggest  the  substitution  of  the  nitrate  for  the 
acetate  of  lead,  as  we  should  then  have,  in  the  liberated 
nitrate  of  potash,  a  valuable  auxiliary  in  the  process  of  pre- 
servation. 

"  Although  highly  desirable,  as  the  demonstrator  of  the 


ON    MINUTE    INJECTIONS.  141 

capillaries  of  normal  tissues,  I  do  not  think  this  kind  of  injec- 
tion fitted  for  morbid  preparations,  the  infiltrated  gelatine 
producing  appearances  of  a  puzzling  kind,  and  calculated  to  mis- 
lead the  pathologist. 

"In  preparing  portions  of  dried,  well-injected  skin,  for  exa- 
mination by  the  microscope,  I  have  tried  the  effect  of  dilute 
nitric  acid,  as  a  corroder,  with  very  good  results.  But,  proba- 
bly, liquor  potassse  would  have  answered  this  purpose  better. 

"When  size  injection  is  to  be  employed,  coloured  either  with 
vermilion  or  the  chromate  of  lead,  the  animal  should  be  pre- 
viously prepared  by  bleeding,  to  empty  the  vessels :  for  if 
they  be  filled  with  coagulated  blood,  it  is  quite  impossible  to 
transmit  even  size,  to  say  nothing  of  the  colouring  matter. 
Hence  the  difficulty  of  procuring  good  injections  of  the  human 
subject. 

"But  with  the  ' chemico-gelatinous'  injections  no  such  pre- 
paration is  necessary ;  and  success  should  always  be  certain,  for 
the  potash  liquefies  the  blood,  while  constant  and  long-con- 
tinued pressure  by  the  syringe  drives  it  through  the  parietes  of 
the  vessel  into  the  cellular  tissue.  The  large  quantity  of  in- 
filtrated blood — the  invariable  concomitant  of  my  process — 
characterizes  this  from  all  other  modes  of  injecting,  and  is  a 
distinctive  feature  of  these  preparations." 

Still  another  plan  has  been  suggested  (as  I  am  informed) 
by  Dr.  G-oddard  of  Philadelphia.  It  consists  in  adding  a 
quantity  of  sulphuric  ether  to  the  finely  levigated  colouring 
matter,  which  is  also  first  ground  or  mixed  with  linseed  oil,  in 
the  manner  employed  by  painters.  Upon  this  plan  (as  well  as 
upon  the  last  named)  I  have  succeeded  in  making  some  beau- 
tiful injections  of  the  smallest  capillaries,  yet  I  have  some- 
times failed,  owing  to  the  too  rapid  evaporation  of  the  ether, 
and  the  clogging  up  of  the  vessels  from  the  early  deposition  of 
the  solid  colouring  matter.  Perhaps  a  solution  of  gum  mas- 


142  THE    MICROSCOPIST. 

tich,  &e.?  in  ether,  coloured  with  fine  vermilion,  &c.,  will  answer 
the  indications  better. 

A  foetus  may  be  injected  by  the  umbilical  vein;  a  uterus, 
by  the  hypogastric  arteries ;  the  head,  by  the  carotids ;  the 
liver,  mucous  membrane  of  the  intestines,  &c.,  by  the  portal 
vein ;  an  extremity,  by  the  principal  artery ;  &c. 

Many  parts,  after  injection,  require  to  be  macerated  in  water, 
or  corroded  by  dilute  muriatic  acid,  &c.,  in  order  to  exhibit  the 
ramifications  of  the  small  vessels.  They  should  be  very  care- 
fully handled,  or  moved,  in  the  macerating  liquor,  as  the  slight- 
est force  may  break  the  vessels.  When  corroded,  the  pulpy 
flesh  is  to  be  carefully  washed  away  by  placing  it  under  a 
stream  of  water,  flowing  very  slowly;  or  by  the  use  of  a  syringe 
with  water. 

The  lymphatics  are  usually  injected  with  quicksilver,  but 
M.  Rusconi  and  Professor  Breschet,  have  abandoned  this  me- 
thod for  the  coloured  material,  on  account  of  the  mercury  fre- 
quently rupturing  by  its  weight  the  thin,  lymphatic  vessels 
and  reservoirs.  The  first-named  gentleman,  in  his  researches 
on  the  lymphatics  of  reptiles,  employs  in  place  of  the  usual 
injecting  tube  of  Walter  (used  with  the  mercury),  a  small 
silver  syringe,  together  with  a  kind  of  trocar,  of  which  the 
canula  is  formed,  from  the  quill  of  the  wing-feather  of  the  quail 
or  partridge,  the  trocar  being  a  tolerably  large-sized  needle, 
the  point  of  which  has  three  facets.  When  desirous  of  in- 
jecting the  lymphatic  system  of  a  lizard,  tortoise,  &c.,  he  re- 
marks : — "  I  seize  with  a  small  pair  of  forceps  the  mesentery, 
close  to  the  vertebral  column,  where  the  reservoir  of  the  chyle 
is  situated,  and  I  introduce  into  it  the  point  of  the  trocar ;  I 
then  retain  the  quill  and  withdraw  the  needle  from  the  tube. 
This  done,  I  seize  with  the  small  forceps  the  quill,  and  intro- 
duce into  it  the  small  extremity  of  the  syringe,  and  push  the 
piston  with  a  force  always  decreasing."  He  recommends 
coloured  wax,  mixed  with  nut-oil,  for  the  injection. 


CHAPTER   XII. 

EXAMINATION    OF    URINARY    DEPOSITS. 

THE  chemical  composition  of  the  urine  and  urinary  deposits 
has  within  a  few  years  past  attracted  much  attention,  and  has 
contributed  much  to  our  knowledge  respecting  the  nature  of 
diseases  and  their  diagnosis.  To  examine  these,  the  microscope 
is  often  an  essential  instrument. 

Deposits  of  uric  acid  and  its  combinations  (called  red,  or 
yellow-sand  sediments),  occur  in  fever;  in  acute  inflammation; 
in  rheumatism ;  in  phthisis ;  in  all  the  grades  of  dyspepsia ; 
in  all  or  most  stages  of  diseases  attended  with  arrest  of  per- 
spiration; in  diseases  of  the  genital  apparatus;  from  blows 
and  strains  of  the  loins ;  from  excessive  indulgence  in  animal 
food ;  or  from  too  little  exercise. 

The  deposition  of  earthy  phosphates  (white  deposit),  should 
be  regarded  as  of  serious  importance,  always  indicating  the 
existence  of  important  functional,  and  frequently  of  organic 
disorder.  According  to  Dr.  Bird,  they  always  exist  simul- 
taneously with  a  depressed  state  of  nervous  energy,  often 
general,  rarely  more  local,  in  its  seat. 

Deposits  of  oxalate  of  lime  are  regarded  by  Dr.  Gr.  Bird  as 
by  no  means  so  rare  as  is  generally  supposed.  He  believes 
that  it  owes  its  origin  to  sugar,  and  is  caused  by  derangement 
of  the  digestive  organs. 

The  urine  may  contain  all  or  any  of  the  elements  of  the 


144  THE    MICROSOOPIST. 

blood.     The  serum  may  be  effused  alone,  or  be  accompanied 
with  the  red  globules. 

Whenever  the  elements  of  blood  appear  in  the  urine,  there 
is  ample  proof  of  the  existence  of  active  or  passive  hemorrhage 
of  the  kidneys,  or  urinary  tract. 

Albuminous  urine  occurs  in  Bright' s  disease,  dropsy  after 
scarlatina,  &c. 

Pus  is  met  with  in  the  urine  as  the  result  of  suppuration  of 
the  kidney,  or  of  some  part  of  the  genito-urinary  mucous  mem- 
brane, or  of  abscesses  of  the  neighbouring  viscera,  opening 
into  the  urinary  passage. 

The  presence  of  sugar  is  not  uncommon  in  dyspepsia,  and 
when  excessive  is  diagnostic  of  diabetes  mellitus. 

Kiestein  is  a  whitish,  greasy,  opalescent  pellicle,  sometimes 
found  on  the  urine  of  pregnant  women. 

To  examine  urinary  deposits  with  the  microscope,  allow  the 
urine  to  stand;  decant  the  supernatant  fluid;  pour  the  re- 
mainder into  a  watch-glass ;  draw  off  the  small  quantity  of 
fluid  remaining  after  a  short  repose,  by  means  of  a  pipette ; 
and  then  place  it  on  the  stage  of  the  microscope.  When,  how- 
ever, it  is  necessary  to  use  high  powers,  a  drop  of  the  sediment 
should  be  placed  on  a  glass  slide  and  covered  with  thin  glass. 

If  it  is  desired  to  mount  the  object  for  future  examination, 
it  can  be  covered,  when  dry,  with  a  drop  of  Canada  balsam, 
and  surmounted  with  the  thin  glass.  Very  transparent  objects 
should  be  kept  in  fluid,  as  weak  spirit,  water  saturated  with 
creasote,  or  Goadby's  fluid. 

HEALTHY  URINE  holds  in  solution  a  variety  of  substances, 
both  organic  and  inorganic.  Chemists  have  not  yet  succeeded 
in  insulating  all  its  ingredients  for  examination,  but  the  most 
important  of  its  solid  materials  are  urea,  uric  acid,  hippuric 
acid,  vesical  mucus  and  epithelial  debris,  animal  extractive, 
ammoniacal  salts,  fixed  alkaline  salts,  and  earthy  salts. 


EXAMINATION    OF    URINARY    DEPOSITS.        145 

The  amount  passed  by  an  individual  during  each  twenty-four 
hours,  varies  from  twenty  to  fifty  ounces,  holding  in  solution 
from  six  hundred  to  seven  hundred  grains  of  solid  matter. 
When  kept  for  some  time  it  gradually  becomes  turbid,  and  de- 
posits a  sediment  of  earthy  phosphates,  previously  held  in 
solution  by  the  slight  excess  of  acid  present.  If  kept  still 
longer,  it  gradually  putrefies,  and,  becoming  concentrated  by 
evaporation,  deposits  small  crystals  of  chloride  of  sodium, 
phosphates,  and  other  salts,  and  eventually  becomes  covered 
with  a  grayish-coloured  mould. 

Urea  appears  to  be  the  vehicle  by  which  nearly  the  whole  of 
the  nitrogen  of  the  exhausted  tissues  of  the  body  is  removed 
from  the  system.  The  proportion  of  urea  in  healthy  urine 
averages  fourteen  or  fifteen  parts  in  the  one  thousand.  Pure 
urea  may  be  obtained  by  first  converting  it  into  the  oxalate, 
which  is  done  by  adding  a  strong  solution  of  oxalic  acid  in  hot 
water,  to  urine  previously  concentrated  to  about  one-eighth  its 
bulk,  and  filtered  to  free  it  from  the  insoluble  sediments  of 
phosphates  and  urates.  The  crystals  of  oxalate  of  urea  thus 
obtained,  a,  Fig.  44,  should  be  dissolved  in  hot  water,  and  the 
solution  treated  with  pulverized  chalk  as  long  as  effervescence 
is  produced.  The  urea  remains  in  solution,  and  may  be  puri- 
fied by  boiling  with  animal  charcoal,  after  which  it  may  be 
crystallized,  in  four-sided  prisms,  by  careful  evaporation. 

Nitrate  of  urea  may  be  obtained  in  crystals,  5,  Fig.  44,  by 
concentrating  urine  to  about  one-half  its  bulk,  and  adding  an 
equal  quantity  of  nitric  acid.  If  urea  be  suspected  in  excess, 
a  drop  of  the  urine,  without  concentration,  may  be  treated  with 
nitric  acid  under  the  microscope. 

The  proportion  of  uric  acid  in  the  healthy  secretion  varies 
from  0-3  to  1-0  in  1000  parts.  Its  forms  will  be  represented 
when  we  treat  of  the  examination  of  urinary  deposits.  It  may 
be  obtained  from  urine  concentrated  to  half  its  bulk,  by  adding 

13 


146 


THE     MICEOSCOPIST. 


a  few  drops  of  hydrochloric  acid,  and  allowing  it  to  stand  a 
few  hours  in  a  cool  place. 


Fig.  44. 


Hippuric  Acid  is  generally  present  in  a  small  quantity  in 
healthy  urine,  and  in  certain  forms  of  disease,  especially  where 
a  vegetable  diet  has  been  adopted.  Fig.  45  represents  some 

Fig.  45. 


of  its  forms ;   a  are  deposited  from  an  alcoholic  solution,  and 
b  from  a  hot  aqueous  solution. 

When  an  excess  is  suspected  in  urine,  it  should  be  evapo- 
rated to  the  consistence  of  syrup  a,nd  mixed  with  half  its  bulk 
of  strong  hydrochloric  acid.  After  a  few  hours  the  crystals 


EXAMINATION    OF    URINARY    DEPOSITS.         147 

may  be  examined  with  the  microscope,  when  the  tufts  will 
probably  be  seen,  coloured  pink  by  the  admixture  of  purpu- 
rine.  If  it  be  present  only  in  small  quantity,  a  few  detached 
needle-like  or  branched  crystals  may  be  seen.  It  is  readily 
soluble  in  alcohol  and  hot  water,  but  not  in  cold  water. 

Vesical  Mucus  and  Epithelial  Scales,  which  may  be  present, 
are  derived  from  the  internal  surface  of  the  bladder  and  uri- 
nary passages.  The  quantity  is  so  small  in  healthy  urine  as  to 
be  scarcely  visible,  until,  after  standing,  it  has  subsided  to  the 
bottom  of  the  liquid  in  the  form  of  a  thin  cloud. 

Extractive  Matter,  includes  all  the  uncrystallizable  organic 
matter  found  in  the  residue  of  evaporated  urine,  which  is 
soluble  in  water  or  alcohol.  When  in  excess,  the  urine  ap- 
pears more  highly  coloured  than  usual,  a.  large  proportion  of 
what  is  termed  extractive,  consisting  of  colouring  matter,  as 
purpurine,  &c. 

Ammoniacal  Salts  appear  to  consist  chiefly  of  the  muriate 
and  the  urate,  the  latter  salt  being  the  form  in  which  the  uric 
acid  present  in  the  urine  appears  to  be  held  in  solution. 

The  proportion  of  ammonia  in  healthy  urine  is  quite  small, 
but  in  some  diseases,  especially  in  certain  kinds  of  fever,  it 
increases  considerably. 

Fixed  Alkaline  Salts  may  be  obtained  by  incinerating  the 
evaporated  residue  of  urine,  when  a  white  ash  will  be  left, 
consisting  of  a  mixture  of  alkaline  and  earthy  salts ;  the  for- 
mer may  be  separated  from  the  latter  by  dissolving  in  water, 
in  which  the  earthy  salts  are  insoluble. 

The  alkaline  salts,  which  in  the  healthy  secretion  usually 
amount  to  thirteen  or  fourteen  parts  in  one  thousand,  consist 
of  the  sulphates  of  potash  and  soda,  chloride  of  sodium,  chlo- 
ride of  potassium,  and  phosphate  of  soda.  The  crystallized 
residue,  after  slowly  evaporating  a  few  drops  on  a  piece  of  glass, 
usually  has  the  appearance  represented  in  Fig.  46.  The  cross- 


148  THE    MIOROSCOPIST. 

lets  consist  of  chloride  of  sodium ;  the  more  plumose  crystals 
are  probably  phosphate  of  soda. 

Fig.  46. 


The  Earthy  Salts  which  form  the  insoluble  portion  of  the 
ash,  and  which  usually  amount  in  healthy  urine  to  about  1 
part  in  1000,  consist  of  the  phosphates  of  lime  and  magnesia, 
together  with  a  small  trace  of  silica.  These  appear  to  be  re- 
tained in  solution  in  the  urine  by  the  small  excess  of  acid 
(probably  phosphoric)  usually  present,  and  may  be  precipitated 
from  it  by  supersaturating  with  ammonia.  The  precipitate 
thus  formed  consists  of  a  mixture  of  phosphate  of  lime,  and 
the  double  phosphate  of  ammonia  and  magnesia,  which  is 
also  called  triple  phosphate.  These,  with  the  abnormal  ingre- 
dients found  in  morbid  urine,  &c.,  will  be  treated  of  when  we 
come  to  the  examination  of  urinary  deposits.  It  must  be 
borne  in  mind,  however,  that  a  spontaneous  precipitate  of 
earthy  phosphates  is  not  of  itself  a  proof  that  they  are  present 
in  excess,  for  when  the  urine  is  acid,  as  in  health,  a  considera- 
ble quantity  may  be  retained  in  solution,  while  if  it  be  neutral 
or  alkaline,  a  comparatively  small  proportion  may  be  precipi- 
tated. 

When  urinary  deposit  is  examined  with  the  microscope,  it 


EXAMINATION    OP    URINARY    DEPOSITS.        149 

will  be  found  either  crystalline,  amorphous,  or  organized. 
When,  as  is  frequently  the  case,  the  deposit  consists  of  a 
mixture  of  different  forms,  each  of  them  in  succession  should 
be  examined,  until  the  nature  of  the  whole  deposit  is  clearly 
understood. 

"CRYSTALLINE  DEPOSITS,  will  probably  be  either  uric  acid, 
phosphate  of  lime  and  magnesia  (from  which  the  triple  phos- 
phate is  formed),  oxalate  of  lime,  or  perhaps  cystine. 

Triple  Phosphate. — This  salt  (called  also  the  double  phos- 
phate of  ammonia  and  magnesia)  is  formed  by  supersaturating 
with  ammonia.  Phosphate  of  lime  is  also  precipitated  by  the 
same  means,  but  may  be  distinguished  by  the  microscope. 
The  crystals  of  the  triple  phosphate  are  stellate  or  triangular 
prisms,  as  seen  in  Fig.  47.  They  disappear  on  the  addition  of 
acetic  acid. 

Uric  (or  Lithic)  Acid. — This  salt,  like  the  earthy  phos- 
phates, exists  in  a  small  quantity  in  healthy  urine,  but  as  the 
proportion  varies  considerably  in  many  forms  of  disease,  its 
determination  when  in  abnormal  quantity,  affords  much  assis- 
tance in  diagnosis. 

It  is  insoluble  in  alcohol,  and  nearly  so  in  dilute  hydro- 
chloric and  sulphuric  acid ;  but  it  combines  with  the  alkalies, 
forming  salts,  which  are  insoluble  or  very  sparingly  soluble  in 
water. 

The  action  of  nitric  acid  upon  uric  acid  is  characteristic.  It 
will  gradually  dissolve  it,  carbonic  acid  and  nitrogen  being 
given  off  with  effervescence,  leaving  behind  a  mixture  of 
alloxan  (C8  N3  H4  010),  alloxantine  (C4  H3  N2  03),  and  other 
compounds.  This  may  be  evaporated  nearly  to  dryness,  when 
a  red  residue  will  be  left,  which,  when  cold,  should  be  moist- 
ened with  ammonia,  which  will  develope  a  beautiful  purple 
colour,  owing  to  the  formation  of  murexide  (Cia  N5  H6  08). 

13* 


150 


THE    MICROSCOPIST. 


The  crystalline  forms  of  uric  acid  are  various,  but  appear  to 
be  modifications  of  the  rhombic  prism. 


Fig.  47. 


Fig.  48  represents  some  of  its  forms. 

Oxalate  of  Lime  often  exists  in  the  form  of  minute  octahe- 
dral crystals,  varying  from  yj^th  to  ygVuth  of  an  inch  in 
diameter,  a,  Fig.  49.  When  allowed  to  dry  on  the  glass,  each 


EXAMINATION    OP    URINARY    DEPOSITS.        151 

crystal  appears  under  the  microscope  like  a  black  cube,  having 

Fig.  48. 


in  the  centre  a  small  white  square  opening,  as  shown  at  b. 


152 


THE     MICROSCOPIST. 


This  is  owing  to  the  rays  of  light  being  mostly  refracted  be- 
yond the  field  of  vision.  On  again  moistening  them,  the  crys- 
tals reappear  in  their  octahedral  form.  Sometimes  this  salt 


Fig.  49. 


assumes  the  forms  represented  at  c;  more  or  less  resembling 
dumb-bells.*     This  form,  like  the  crystals  of  uric  acid,  the 

*  Dr.  Fricke,  in  the  American  Journal  of  Medical  Science,  July, 
1850,  states  as  his  opinion  that  the  dumb-bell  forms  of  crystals  are 
not  oxalate  of  lime,  but  disintegrated  crystals  of  uric  acid. 


EXAMINATION    OF    URINARY    DEPOSITS.        153 

triple  phosphate,  &c.,  is  beautifully  coloured  when  examined 
by  polarized  light;  the  octahedral  variety  has  little  or  no  effect 
upon  it,  being  invisible,  or  nearly  so,  when  the  field  is  dark. 
If  the  "  dumb-bells"  are  kept  in  liquid  for  any  length  of  time, 
they  gradually  pass  into  octahedra. 

As  the  crystals  of  oxalate  of  lime  are  very  transparent,  and 
about  the  same  specific  gravity  as  the  urine,  they  may  readily 
escape  detection,  unless  some  considerable  time  is  allowed  for 
deposition,  or  the  urine  is  passed  through  a  filter. 

Oxalate  of  lime  is  insoluble  in  water,  in  acetic  and  oxalic 
acids,  and  in  solution  of  potash ;  but  it  is  readily  soluble  in 
dilute  nitric  and  hydrochloric  acids. 

Cystine  has  occasionally  been  found  as  a  crystalline  deposit 
and  in  the  form  of  small  calculi.  It  may  be  distinguished  by 
being  insoluble,  or  nearly  so,  in  water  and  dilute  acids,  but 
soluble  in  ammonia,  from  which  small  hexagonal  crystals  are 
deposited  on  evaporation.  The  usual  microscopic  appearance 
is  represented  at  a,  Fig.  50.  At  b  is  the  form  left  from  the 
ammoniacal  solution. 

Fig.  50. 


o33?  (?) 

^ 
O 


AMORPHOUS  DEPOSITS  consist  probably  of  phosphate  of 
lime,  urate  of  ammonia,  urate  of  soda,  fat,  or  chylous  matter. 

Phosphate  of  Lime. — This  salt  has  already  been  described 
as  existing  in  urine  in  conjunction  with  the  phosphate  of  mag- 
nesia. It  is  thrown  down,  together  with  the  triple  phosphate 


154  TrfE    MICROSCOPIST. 

(before  noticed),  on  the  addition  of  ammonia.  The  crystalline 
shape  of  the  triple  phosphate,  however,  readily  distinguishes 
it  under  the  microscope  from  the  amorphous  particles  of  phos- 
phate of  lime  with  which  it  is  usually  mixed.  The  earthy 
phosphates  are  readily  soluble  in  dilute  acids,  from  which  they 
are  precipitated  by  ammonia.  They  are  insoluble  in  a  solution 
of  potash. 

Urate  of  Ammonia  constitutes  one  of  the  most  common 
urinary  deposits.  It  is  gradually  deposited  as  the  urine  cools, 
in  the  form  of  an  amorphous  precipitate,  which,  with  a  high 
magnifying  power,  appears  to  consist  of  minute  rounded  par- 
ticles, occasionally  adhering  together,  frequently  mixed  with 
small  crystals  of  uric  acid,  and  occasionally  with  the  earthy 
phosphates.  A  deposit  of  urate  of  ammonia  readily  dissolves 
when  the  urine  containing  it  is  gently  warmed,  and  is  preci- 
pitated again  when  the  liquid  cools.  (The  earthy  phosphates 
and  uric  acid  are  nearly  as  insoluble  in  hot  as  cold  water.) 

When  urate  of  ammonia  is  treated  with  dilute  acetic  or 
hydrochloric  acid,  it  is  decomposed,  and  uric  acid  is  formed. 

Urate  of  Soda  is  often  met  with  in  the  urine  of  patients 
taking  medicinally  the  carbonate  or  other  salts  of  soda.  It  re- 
sembles the  urate  of  ammonia  in  being  soluble  in  hot  water, 
and  in  most  of  its  chemical  characters,  but  may  be  generally 
recognised  without  difficulty  under  the  microscope,  forming 
minute  globular  or  granular  aggregations,  with,  occasionally, 
irregular  and  curved  protuberances. 

Fat  may  be  recognised  by  the  particles  being  minute  round 
globules,  with  dark  and  well-defined  outlines,  which  dissolve 
when  agitated  with  ether. 

Sometimes  this  substance  is  mixed  with  albuminous  matter, 
forming  a  kind  of  emulsion,  so  that  no  trace  of  fat  can  be 
perceived  with  the  microscope.  In  such  cases,  the  urine  may 
be  agitated  with  a  little  ether,  which  will  dissolve  the  fat,  and 


EXAMINATION    OF    URINARY    DEPOSITS.        155 

the  solution  so  formed  will  separate  from  the  watery  liquid, 
and  form  a  distinct  stratum  on  the  surface. 

Chylous  Matter  may  be  known  by  the  urine  being  opaque 
and  milky  in  appearance,  yielding  fatty  matter  when  agitated 
with  ether,  and  containing  minute,  amorphous,  albuminous 
particles,  and  perhaps  also  colourless  globules,  which  may 
possibly  be  mistaken  for  oil  globules,  from  which  their  insolu- 
bility in  ether  distinguishes  them. 

ORGANIZED  DEPOSITS  may  either  be  mucus,  usually  mixed 
with  epithelium ;  pus ;  blood ;  or  semen. 

Mucus. — If  the  particles  observed  with  the  microscope  are 
round,  or  nearly  so,  and  granulated  on  the  surface,  entangled 
in  tenacious,  stringy  masses,  which  do  not  break  up  and  mix 
uniformly  with  the  liquid  on  agitation,  it  is  probably  mucus. 

Epithelial  debris  may  be  recognised  by  the  peculiar  form  of 
its  particles.  Mucous  urine  generally  contains  a  considerable 
amount  of  earthy  phosphates  and  other  matters. 

Pus  may  be  known  by  the  particles  not  being  held  together 
by  any  tenacious  matter,  but  floating  freely  in  the  liquid.  The 
granules  of  pus  and  mucus  present  almost  the  same  appear- 
ance under  the  microscope,  although  the  latter  may  probably 
be  rather  smaller  and  less  distinctly  granular.  Acetic  acid 
renders  the  interior  nuclei  visible  in  both,  but  it  coagulates 
the  fluid  portion  of  the  mucus. 

Even  this  test  may  be  uncertain,  on  account  of  the  dilution 
of  the  mucous  fluid,  and  also  because  the  coagulation  may 
have  been  already  occasioned  by  the  presence  of  the  large 
quantity  of  water.  When  the  quantity  of  mucus  is  abundant, 
however,  this  test  will  be  sufficient. 

Blood. — When  this  is  suspected  in  the  urine,  it  may  be 
examined  under  the  microscope  for  any  blood  corpuscles  that 
may  be  in  it.  If  the  blood  has  coagulated,  they  will  proba- 
bly be  entangled  in  the  coagula,  and  may  be  forced  out  by 


156  THE     MICROSCOPIST. 

gentle  pressure  under  a  strip  of  thin  glass.  If  there  is  no 
coagula,  the  liquid  may  rest  for  a  short  time,  and  a  drop  from 
the  bottom  examined.  The  urine  may  also  be  tested  for 
albumen  after  separating  the  solid  matter  by  filtering.  When 
the  colouring  matter  of  the  blood  is  present,  it  will  coagulate 
with  the  albumen,  giving  it  a  red  or  brown  colour.  When  the 
fibrin,  in  its  soluble  form,  is  present,  it  usually  coagulates 
spontaneously  on  cooling,  causing  the  urine  to  become  gelati- 
nous. The  coagulum  of  fibrin,  when  pressed  between  glasses, 
is  generally  composed  of  minute  amorphous  particles,  with  a 
few  red  blood  corpuscles,  quite  different  from  the  granular 
mucus  corpuscles,  for  which  it  might  be  mistaken  without 
microscopic  examination. 

Bile  or  purpurine  in  urine  has  nearly  the  same  colour  as 
when  blood  is  present ;  hence,  unless  the  blood  corpuscles  are 
present,  we  should  apply  the  tests  for  the  detection  of  those 
substances  before  finally  deciding.  Purpurine  will  be  dissolved 
by  treating  with  warm  alcohol,  or  may  be  precipitated  by  add- 
ing a  little  warm  aqueous  solution  of  urate  of  ammonia,  which 
on  cooling  will  fall  down,  carrying  with  it  the  colouring  mat- 
ter. Bile  may  be  tested  by  pouring  a  few  drops  of  urine  on  a 
white  plate,  and  adding  carefully  a  drop  or  two  of  nitric  acid. 
When  bile  is  present  in  any  considerable  quantity,  the  liquid 
becomes  successively  pale-green,  violet,  pink,  and  yellow,  the 
colour  rapidly  changing  as  the  acid  mixes  with  the  urine. 
When  only  slight  traces  of  bile  are  present,  the  urine  should 
be  concentrated  by  evaporation. 

When  semen  is  present  in  urine,  it  may  easily  be  detected 
under  the  microscope,  by  the  appearance  of  minute  animalcu- 
les, always  found  in  the  spermatic  fluid,  and  hence  called  sper- 
matozoa. They  are  oval  in  shape,  with  long  and  delicate  tails. 
Traces  of  albumen  may  generally  be  detected  in  urine  contain- 
ing semen. 


EXAMINATION    OF    URINARY    DEPOSITS.        157 

DIABETIC  AND  ALBUMINOUS  URINE. — Albumen  may  be 
tested  by  boiling  the  suspected  urine  gently  in  a  test-tube, 
when  it  will  be  coagulated.  As,  however,  a  white  precipitate 
results  on  boiling,  from  an  excess  of  earthy  phosphates,  it  will 
be  necessary  to  add  a  few  drops  of  nitric  acid,  which  will  re- 
dissolve  the  phosphates  but  leave  the  coagulated  albumen  un- 
affected. Nitric  acid  also  will  coagulate  albumen.  If  both 
heat  and  nitric  acid  throw  down  a  white  precipitate  from  urine 
in  separate  portions,  there  can  be  no  doubt  of  the  presence  of 
albumen. 

The  peculiar  casts  of  urinary  tubes  found  in  the  urine  of 
patients  suffering  from  Bright' s  disease,  consist  of  fibrinous  or 
albuminous  matter  and  entangling  blood-corpuscles,  epithelium, 
and  fatty  globules. 

Diabetic  Sugar  has  the  same  chemical  composition  as  that 
contained  in  most  kinds  of  fruit,  known  as  grape  sugar.  Se- 
veral tests  have  been  proposed  for  its  detection  in  urine. 

Trommer's  Test  is  founded  on  the  circumstance  that  when  a 
solution  of  diabetic  or  grape  sugar  is  boiled  with  a  mixture  of 
potash  and  sulphate  of  copper,  the  oxide  of  copper  contained 
in  the  latter  is  reduced  to  the  state  of  suboxide,  which  is  pre- 
cipitated in  the  form  of  a  reddish-brown  or  ochre-coloured 
granular  powder. 

Moore's  Test  is  made  by  mixing  a  little  suspected  urine  with 
half  its  volume  of  liquor  potassse  and  boiling  gently  for  about 
five  minutes.  If  sugar  is  present,  the  liquid  assumes  a  brown 
or  bistre  tint. 

The  Fermentation  Test  is  made  by  filling  a  test-tube  with 
the  suspected  urine,  to  which  a  little  yeast  has  been  added. 
The  tube  is  then  inverted  over  a  saucer  containing  some  of  the 
urine,  and  set  aside  in  a  warm  place  for  about  twenty-four 
hours.  If  sugar  is  present  it  undergoes  the  vinous  fermenta- 
tion by  which  it  becomes  converted  into  alcohol  and  carbonic 

14 


158  THE     MICROSCOPIST. 

acid.  The  latter  rises  in  the  tube  and  displaces  the  liquid.  If 
no  sugar  be  present,  no  fermentation  will  take  place,  and  no 
gas  will  be  formed  in  the  tube. 

Test  from  the  Growth  of  the  Torula. — During  the  process  of 
the  vinous  fermentation  of  a  liquid  containing  sugar,  a  delicate 
white  scum  collects  on  the  surface,  which  when  examined  with 
a  magnifying  power  of  four  or  five  hundred  diameters,  will  be 
found  to  consist  of  small,  oval  vesicles,  a,  Fig.  51,  which,  in 


Fig.  51. 


the  course  of  a  few  hours,  rapidly  change  their  form,  becoming 
longer  and  more  tubular,  and  give  rise  to  new  vesicles,  which 
shoot  out  from  the  parent  body,  forming  an  irregular  jointed 
confervoid  stem,  fr.  These  again  break  up  into  a  great  num- 
ber of  oval  vesicles,  which  separate,  and  fall  to  the  bottom, 
where  they  may  be  detected  by  the  microscope. 

The  following  tables  for  facilitating  the  examination  of 
urine  and  urinary  deposits,  are  modified  from  Bowman's  Me- 
dical Chemistry.  The  reader  may  also  consult  the  Manuals  of 
Drs.  Golding  Bird,  Griffith,  Markwick,  and  Rees.  The  works  of 
the  latter  three  gentlemen  have  been  published  in  Philadelphia, 
in  one  convenient  volume.  The  "  Analysis"  of  Dr.  Rees  con- 
tains also  a  valuable  essay  on  the  treatment  of  urinary  dis- 
eases. 


EXAMINATION    OF    URINARY    DEPOSITS.        159 


TABLE    I. 

FOR    THE    CHEMICAL     EXAMINATION    OF     URINARY 
DEPOSITS. 

1.  The  sediment  dissolves  when  warmed.      Urate  of  Am- 
monia. 

2.  Not  soluble  when  warmed,  but  soluble  in  acetic  acid. 
Earthy  Phosphates. 

3.  Insoluble  in  acetic,  but  soluble  in  dilute  hydrochloric 
acid.      Oxalate  of  Lime. 

4.  Insoluble  in  dilute  hydrochloric  acid.    Purple  with  nitric 
acid  and  ammonia.      Uric  Acid. 

If  neither  of  these,  it  may  be, 

5.  Greenish-yellow   deposit,    easily   diffused   on    agitation. 
Pus? 

6.  Ropy  and  tenacious.     Mucus? 

7.  Red  or  brown;  not  soluble  when  warmed;  the  fluid  por- 
tion coagulable  by  heat  and  nitric  acid.     Blood? 

8.  Soluble  in  ammonia;  the  solution  leaving,  on  evaporation, 
hexagonal  crystals.      Cystine? 

9.  Yellowish    sediment,   soluble  when  warmed.      Urate  of 
Soda? 

10.  Ether  yields,  after  agitation,  an  oily  or  fatty  residue. 
Fatty  Matter. 

11.  Milky  appearance.      Ghylous  Matter. 

TABLE  II. 

FOR    THE    EXAMINATION    OF    THE    CLEAR    LIQUID 
PORTION. 

1.  Crystals  with  nitric  acid.     Excess  of  Urea. 

2.  Fermentation,  or  Trommer's  test.     Sugar. 


160  THE    MICROSCOPIST. 

3.  Precipitate   formed  on  boiling;    soluble  in  nitric  acid. 
Excess  of  Earthy  Phosphates. 

4.  Precipitate  formed  on  boiling;  insoluble  in  nitric  acid. 
Albumen. 

5.  Precipitate  formed  by  nitric  acid.     Excess  of  Uric  Acid, 
or  Albumen. 

6.  Concentrated  urine  yields   needle-shaped  crystals  with 
hydrochloric  acid.     Hippuric  Acid. 

If  the  urine  is  highly  coloured, 

7.  Dark  coagulum  formed  on  boiling.     Blood  f 

8.  Red  colour  with  hydrochloric  acid.     Excess  of  Colouring 
Matter. 

9.  Pink  precipitate  with  warm  solution  of  urate  of  ammonia. 
Purpurine. 

10.  Change  of  colour  with  nitric  acid.    Biliary  Matter. 


TABLE   III. 
FOE    MICROSCOPIC    EXAMINATION    OF    DEPOSIT. 

If  Crystalline. 

1.  Lozenge-shaped,  &c.     Uric  Acid. 

2.  Stella,  or  three-sided  prisms  (after  saturating  with  am- 
monia).     Triple  Phosphate. 

3.  Octahedra,  or  dumb-bells.      Oxalate  of  Lime. 

4.  Rosette-like  tables.     Cystine. 

If  Amorphous. 

5.  Soluble  when  warmed.      Urate  of  Ammonia. 

6.  Soluble  in  acetic  acid.     Phosphate  of  Lime. 

7.  Yellowish  grains.      Urate  of  &oda  ? 


EXAMINATION    OF    URINARY    DEPOSITS.        161 

8.  Bound  globules  with  dark  edges.     Fatty  Matter. 

9.  White  and  milky.      Cliylous  Matter? 

If  Organized. 

10.  Granulated  corpuscles,  in  stringy  aggregations.    Mucus. 

11.  Irregularly  shaped  scales.     Epithelium. 

12.  Detached  granulated  corpuscles.     Pus. 

13.  Blood-corpuscles.     Blood. 

14.  Spermatozoa.     Semen. 


14* 


CHAPTER   XIII. 


ON    POLARIZED    LIGHT. 


"  IF  we  transmit,"  says  Dr.  Brewster,  "  a  beam  of  the  sun's 
light  through  a  circular  aperture  into  a  dark  room,  and  if  we 
reflect  it  from  any  crystallized  or  uncrystallized  body,  or  trans- 
mit it  through  a  thin  plate  of  either  of  them,  it  will  be  re- 
flected and  transmitted  in  the  very  same  manner  and  with  the 
same  intensity,  whether  the  surface  of  the  body  is  held  above 
or  below  the  beam,  or  on  the  right  side  or  left,  or  on  any  other 
side  of  it,  provided  that  in  all  these  cases  it  falls  upon  the 
surface  in  the  same  manner,  or,  what  amounts  to  the  same 
thing,  the  beam  of  solar  light  has  the  same  properties  on  all 
its  sides ;  and  this  is  true,  whether  it  is  white  light  as  directly 
emitted  from  the  sun,  or  whether  it  is  red  light,  or  light  of 
any  other  colour. 

"The  same  property  belongs  to  light  emitted  from  a  candle, 

Fig.  52. 


or  any  burning  or  self-luminous  )}ody,  and  all  such  light  is 
called  common  light.     A  section  of  such  a  beam  of  light  will 


ON    POLARIZED    LIGHT.  163 

be  a  circle,  like  A,  B,  C,  D,  Fig.  52,  and  we  shall  distinguish 
the  section  of  a  beam  of  common  light  by  a  circle  with  two 
diameters,  AB,  CD,  at  right  angles  to  each  other. 

"If  we  now  allow  the  same  beam  of  light  to  fall  upon  a 
rhomb  of  Iceland  spar,  as  in  Fig.  53,  and  examine  the  two 


circular  beams,  0  0,  E  e,  formed  by  double  refraction,  we  shall 
find, 

"  1.  That  the  beams  0  o,  E  e,  have  different  properties  on  dif- 
ferent sides;  so  that  each  of  them  differs,  in  this  respect,  from 
the  beam  of  common  light. 

"  2.  That  the  beam  0  o  differs  from  E  e  in  nothing,  excepting 
that  the  former  has  the  same  properties  at  the  sides  A'  and  B'" 
that  the  latter  has  at  the  sides  C'  and  D',  as  shown  in  Fig.  52 ; 
or,  in  general,  that  the  diameters  of  the  beam,  at  the  extremi- 
ties of  which  the  beam  has  similar  properties,  are  at  right 
angles  to  each  other. 

"These  two  beams,  Oo,  Ee,  Fig.  53,  are  therefore  said  to  be 
polarized,  or  to  be  beams  of  polarized  light,  because  they  have 
sides  or  poles  of  different  properties. 

"Now  it  is  a  curious  fact,  that  if  we  cause  the  two  polarized 
beams,  0  o,  E  e,  Fig.  53,  to  be  united  into  one,  we  obtain  a 
beam  which  has  exactly  the  same  properties  as  the  beam  A,  B, 
C,  D,  Fig.  52,  of  common  light.  Hence  we  infer,  that  a  beam 


164  THE    MICROSCOPIST. 

of  common  light  consists  of  two  beams  of  polarized  light, 
whose  planes  of  polarization,  or  whose  diameters  of  similar 
properties,  are  at  right  angles  to  one  another." 

There  are  other  means  of  polarizing  light  besides  that  of 
double  refraction,  just  mentioned.  M.  Malus  discovered,  in 
1810,  that  a  beam  of  common  light,  reflected  from  glass  at  an 
angle  of  56°,  or  from  water  at  an  angle  of  53°  became  polar- 
ized. 

In  order  to  explain  the  phenomena  of  polarized  light  when 
produced  by  reflection  from  glass,  let  C,  D,  Fig.  54,  represent 

Fig.  54. 


two  tubes,  one  turning  within  the  other.  A,  B,  are  plates  of 
glass  capable  of  turning  on  their  axis,  so  as  to  form  different 
angles  with  the  axis  of  the  tube. 

If  a  beam  of  ligjit,  f  s,  from  a  candle  or  hole  in  the  window- 
shutter,  fall  upon  A  at  the  polarizing  angle  of  56°  45',  it  will 
be  reflected  through  the  tubes,  and  will  fall  upon  the  second 
plate,  B,  also  at  an  angle  of  56°  45'.  If,  however,  this  plate 
be  so  placed  that  its  plane  of  reflection  is  at  right  angles  to 
the  plane  of  reflection  of  the  first  plate,  A,  the  ray  of  light 
will  not  suffer  reflection  from  B,  or  will  be  so  faint  as  to  be 
scarcely  visible.  If  we  now  turn  round  the  tube,  D,  carrying 
the  plate,  B,  without  moving  the  tube,  C,  the  reflected  ray,  E, 
will  become  brighter  and  brighter  till  the  tube  has  been  turned 
round  90°,  when  the  plane  of  reflection  from  B  is  coincident  with 


ON    POLARIZED    LIGHT.  165 

or  parallel  to  that  from  A.  In  this  position  the  reflected  ray,  E, 
is  brightest.  If  the  tube  be  turned  again,  the  light  will  grow 
more  and  more  faint,  until  another  90°  are  arrived  at,  when  it 
will  again  undergo  reflection.  Thus,  changes  will  take  place  in 
every  quadrant  of  90°  until  the  starting-point  is  again  reached, 
the  ray  of  light  being  alternately  faint  and  visible. 

The  same  effect  will  be  produced  if  we  cause  a  ray  of  light, 
R,  Fig.  55,  to  pass  through  bundles  of  glass  plates,  A,  B,  in- 

Fig.  55. 


clined  at  the  proper  angle.  If  the  bundle  of  plates,  B,  be 
placed  as  in  the  figure,  the  ray,  s  t,  polarized  by  passing 
through  the  bundle,  A,  will  be  incident  on  B  at  the  polarizing 
angle,  and  not  a  particle  will  be  reflected,  but  it  will  be  trans- 
mitted, as  seen  at  v  w.  If  B  is  now  turned  round  its  axis, 
the  transmitted  light,  v  w,  will  gradually  diminish,  and  more 
and  more  light  will  be  reflected  by  the  plates  of  B,  till,-  after 
a  rotation  of  90°,  the  ray,  v  w,  will  disappear,  and  all  the 
light  will  be  reflected.  Alternate  transmissions  and  reflections 
will  thus  take  place  in  each  quadrant,  as  in  the  former  case. 
For  the  ray  passing  through  the  tube  in  Fig.  54,  or  the  ray, 
s  t,  in  the  last  figure,  we  may  substitute  one  of  the  polarized 
rays  formed  by  double  refraction  in  a  rhomb  of  Iceland  spar, 
as  seen  in  Fig.  53,  or  we  may  employ  with  even  greater  ad- 
vantage the  single  image  prism  of  Mr.  Nicol,  who  employed  a 
rhomb  of  calcareous  spar  divided  into  two  equal  portions,  in  a 
plane  passing  through  the  acute  lateral  angles,  and  nearly 
touching  the  obtuse  solid  angles.  The  cut  surfaces  having  been 
carefully  polished,  were  then  cemented  together  with  Canada 


166  THE     MICROSCOPIST. 

balsam,  so  as  to  form  a  rhomb  of  nearly  the  same  size  and 
shape  as  it  was  before  cutting. 

By  this  arrangement,  of  the  two  rays  into  which  a  beam  of 
common  light  would  be  separated,  only  one  is  transmitted,  the 
other  being  rendered  too  divergent.  Two  of  these  prisms  form 
the  usual  polarizing  apparatus  of  the  microscope,  being  used  in 
the  same  manner  as  the  bundles  of  glass  plates,  Fig.  55,  just 
described.  One  of  the  prisms  is  adapted  to  the  under  surface 
of  the  stage,  and  is  called  the  polarizer ;  the  other,  called  the 
analyzer p,  is  placed  above  the  eye-glass. 

Dr.  Brewster  recommends  that  the  analyzing  prism  be  placed 
immediately  behind  the  object-glass,  next  the  eye,  having  a 
rotation  independent  of  the  body  of  the  microscope. 

Another  method  of  polarizing  light,  is  to  disperse  or  absorb 
one  of  the  oppositely-polarized  beams  which  constitute  common 
light,  and  leave  the  other  beam  polarized  in  one  plane.  These 
effects  may  be  produced  by  thin  plates  of  agate,  tourmaline, 
&c. 

Many  persons  employ  a  thin  plate  of  tourmaline  as  an 
analyzer  in  place  of  a  Nicol's  prism,  and  if  its  colour  be  not 
objectionable,  it  may  be  used  to  advantage,  as  the  field  of 
view  is  not  so  much  contracted  as  when  a  prism  is  used.  A 
tourmaline  of  ameutral  tint  is  an  excellent  analyzer. 

The  splendid  colours,  and  systems  of  coloured  rings,  pro- 
duced by  transmitting  polarized  light  through  transparent 
bodies  that  possess  double  refraction,  are  the  most  brilliant 
phenomena  that  can  be  exhibited.  They  were  discovered 
simultaneously  by  M.  Arago  and  Dr.  Brewster. 

To  see  these  colours : — having  the  polarizing  apparatus  so 
placed  that  no  light  can  be  seen  through  it,  place  a  thin  film 
of  mica  or  sulphate  of  lime  (between  the  twentieth  and  fiftieth 
of  an  inch  thick),  so  that  the  polarized  beam  may  pass  through 
it  perpendicularly.  It  should  be  placed  between  the  polarizer 


ON    POLARIZED    LIGHT.  167 

and  the  analyzer -,  as  on  the  stage  of  the  microscope.  If  now 
the  eye  is  applied  to  the  polarizing  apparatus,  as  before,  the 
surface  of  the  film  of  sulphate  of  lime,  &c.,  will  be  seen 
covered  with  the  most  brilliant  colours.  If  the  film  be  turned 
round,  still  keeping  it  perpendicular  to  the  polarized  ray,  the 
colours  will  become  less  or  more  bright,  and  two  positions  will 
be  found,  at  right  angles  with  each  other,  wherein  no  colours 
at  all  are  perceived.  If  the  analyzer  be  turned  round,  the  film 
retaining  its  position,  complementary  colours  will  alternate, 
together  with  points  of  invisibility,  during  each  revolution. 

The  colours  of  the  film  vary  with  its  thickness,  so  that  by 
making  grooves  or  lines  of  various  depths,  the  most  beautiful 
patterns  may  be  produced.  Drawings  of  figures  and  land- 
scapes are  thus  executed,  and  being  mounted  between  glasses 
in  Canada  balsam,  are  invisible,  or  nearly  so,  till  exposed  to 
polarized  light,  when  they  are  seen  distinctly,  arrayed  in  most 
gorgeous  colours. 

Various  crystals  exhibit,  round  their  axes  of  double  refrac- 
tion, beautiful  systems  of  coloured  rings,  often  intersected  by 
a  black  cross.  Complementary  colours  may  be  produced  in 
them  by  turning  round  the  analyzer.  In  large  crystals,  as 
rhombs  of  Iceland  spar,  certain  angles  must  be  ground  down 
and  polished  in  order  to  exhibit  the  rings. 

In  those  crystals  having  two  axes  of  double  refraction,  a 
double  system  of  rings  will  be  seen.  A  transverse  section  of 
a  prism  of  nitre  will  exhibit  this  phenomenon. 

The  great  advantage  of  employing  the  microscope  in  viewing 
the  colours  of  crystals,  &c.,  by  polarized  light,  arises  from  the 
fact  that,  when  crystallized  on  a  slip  of  glass,  many  of  the 
small  crystals  will  be  arranged  with  their  axes  of  double  re- 
fraction in  the  direction  of  the  polarized  beam.  All  such, 
therefore,  will  exhibit  colours,  as  will  those  also  in  which  the 
thickness  of  the  crystal  is  not  below  the  proper  standard. 


168  THE    MICROSCOPIST. 

After  the  polarizing  apparatus  is  adjusted,  as  before  de- 
scribed, the  crystals,  properly  mounted,  may  be  placed  on  the 
stage,  in  the  same  way  as  ordinary  objects.  Some  few  vege- 
table structures  may  be  exhibited  in  the  same  manner,  as  the 
siliceous  cuticle  of  equisetum,  starch,  &c.  Many  animal 
structures,  as  feathers,  slices  of  quill,  horn,  &c.,  are  best  shown 
by  placing  a  film  of  selenite  or  mica  beneath  them,  by  which 
they  become  intensely  coloured.  If  the  film  be  of  unequal 
thickness,  the  colours  will  vary. 

"The  application,"  says  Mr.  Quekett,  "of  this  modification 
of  light  to  the  illumination  of  very  minute  structures  has  not 
yet  been  fully  carried  out,  but  still  there  is  no  test  of  diffe- 
rences in  density  between  any  two  or  more  parts  of  the  same 
substance  that  can  at  all  approach  it  in  delicacy.  All  struc- 
tures, therefore,  belonging  either  to  the  animal,  vegetable,  or 
mineral  kingdom,  in  which  the  power  of  unequal  or  double 
refraction  is  suspected  to  be  present,  are  those  that  should  es- 
pecially be  investigated  by  polarized  light.  Some  of  the  most 
delicate  of  the  elementary  tissues  of  animals,  such  as  the  tubes 
of  nerves,  the  ultimate  fibrillae  of  muscle,  &c.,  are  amongst 
some  of  the  most  striking  subjects  that  may  be  studied  with 
advantage  under  this  method  of  illumination/' 

To  Prepare  Crystals  for  Polarized  Light.  —  Pour  a  few 
drops  of  a  saturated  solution  of  the  salt  on  a  glass  slide 
gently  warm  it  over  a  spirit  lamp,  so  as  to  evaporate  the 
excess  of  fluid,  taking  care  not  to  apply  too  much  heat,  lest 
the  water  of  crystallization  be  driven  off  and  the  salt  become 
opaque.  The  more  slowly  the  crystallization  is  effected  the 
better. 

The  crystals  should  then  be  examined,  and  the  best  of  them 
mounted,  either  in  the  dry  way  (interposing  a  cell  of  paper, 
&c.,  to  preserve  them  from  injury  by  the  pressure  of  the  glass 
cover),  or  in  Canada  balsam.  If  it  be  desired  to  examine  the 


ON    POLARIZED    LIGHT.  169 

crystals  during  their  formation,  the  crystallization  should  be 
carried  on  in  a  glass  that  is  slightly  concave.  All  those  crys- 
tals that  are  so  thin  as  not  to  exhibit  colour,  may  have  colour 
given  them  by  placing  a  film  of  mica  or  selenite  under  them 
on  the  stage  of  the  microscope. 

According  to  Mr.  Fox  Talbot,  who  first  applied  the  micro- 
scope to  the  examination  of  polarized  light,  sulphate  of  copper, 
crystallized  from  a  solution  to  which  a  little  nitric  ether  has 
been  added ;  oxalate  of  chromium  and  potash,  from  an  aqueous 
solution ;  and  borax,  crystallized  in  dilute  phosphoric  acid,  are 
especially  beautiful. 


15 


CHAPTER  XIV. 


MISCELLANEOUS  HINTS  TO  MICRO  SCOPIST  S. 

ON  CLEANING  THE  GLASSES. — "  When  you  clean  the  eye- 
glasses (a  point  of  great  importance  to  pure  vision),  do  not 
remove  more  than  one  at  a  time,  and  be  sure  to  replace  it  be- 
fore you  begin  another;  by  this  means  you  will  be  sure  to 
preserve  the  component  glasses  in  their  proper  places ;  recol- 
lect that  if  they  become  intermingled,  they  will  be  useless. 
Keep  a  piece  of  well-dusted  chamois  leather,  slightly  impreg- 
nated with  some  of  the  finest  putty  or  crocus  powder,  in  a 
little  box  to  wipe  them  with — for  it  is  of  consequence  to  pre- 
serve it  from  dust  and  damp ;  the  former  will  scratch  the 
glasses,  and  the  latter  will  prevent  you  from  wiping  them 
clean.  As  to  the  object-glasses,  endeavour  to  keep  them  as 
clean  as  possible  without  wiping,  and  merely  use  a  camel' s-hair 
pencil  to  brush  them  with ;  for  wiping  them  hard  with  any- 
thing has  always  a  tendency  to  destroy  their  adjustment, 
unless  they  are  firmly  burnished  into  their  cells. " — Dr.  Goring. 

ON  STOPPING  FALSE  LIGHT  IN  MICROSCOPES. — This  is  one 
of  the  most  important  requisites  in  an  instrument ;  for  how- 
ever perfect  it  may  be,  if  there  is  the  least  light  reflected  from 
the  mountings  of  the  glasses,  or  within  the  tubes,  the  fog  and 
glare  produced  will  materially  deteriorate  their  performance ; 
it  is  therefore  necessary  that  all  their  surfaces  be  made  as 
sombre  as  possible.  The  usual  method  of  effecting  this  is  to 


MISCELLANEOUS    HINTS    TO    MICRO  SCOPIST  S.    171 

cover  the  parts  while  hot  with  a  black  lacquer,  made  by  mix- 
ing lampblack  in  a  solution  of  shell-lac  in  strong  spirits  of 
wine.  A  more  elegant  method,  and  better  suited  for  delicate 
work,  is  to  wash  the  surface,  previously  freed  from  grease  and 
tarnish,  with  a  solution  of  platina  in  nitro-muriatic  acid 
(chloride  of  platinum);  after  remaining  on  the  work  a  few 
minutes  it  is  wiped  off,  the  surface  having  assumed  a  deep 
brown  or  black  colour.  If  these  are  not  at  hand,  a  strong 
solution  of  muriate  of  ammonia  will  answer  for  temporary 
purposes.  Another  method  of  stifling  false  light  is  by  stops  or 
diaphragms  in  the  body  of  the  instrument ;  these  have  already 
been  referred  to. 

CABINET  FOR  MICROSCOPIC  OBJECTS. — The  author  of  "Mi- 
croscopic Objects"  recommends  a  cabinet  with  shallow  draw- 
ers— twelve  of  them  occupy  a  depth  of  four  and  a  half  inches — 
the  most  convenient  width  from  front  to  back  being  six  inches. 
Into  these  shallow  drawers  the  slides  containing  the  objects 
are  laid  flat  in  double  rows.  The  outer  ends  of  the  slides  are 
made  to  fit  into  a  ledge  in  the  front  and  back  of  each  drawer. 
The  inner  ends  of  the  sliders  meeting  in  the  middle  of  the 
drawer  are  kept  down  by  a  very  thin  slip  of  wood  covered  with 
velvet.  In  this  way  the  sliders  do  not  shake  when  the  cabinet 
is  moved  from  place  to  place;  every  object  is  seen  without 
removal,  and  no  loss  of  time  is  occasioned  in  making  a  selec- 
tion. 

Some  persons  have  their  sliders  arranged  edgewise,  in  boxes 
made  in  imitation  of  books ;  the  ends  of  the  sliders  being  held 
by  a  sort  of  rack.  This  may  sometimes  be  convenient,  but  the 
other  form  is  preferable. 

BREWSTER'S  METHOD  OF  ILLUMINATING  OBJECTS. — Con- 
sidering a  perfect  microscope  as  consisting  of  two  parts,  viz., 
an  illuminating  apparatus,  and  a  magnifying  apparatus,  Sir 
D.  Brewster  states,  that  it  is  of  more  consequence  that  the 


172  THE    MICROSCOPIST. 

illuminating  apparatus  should  be  perfect,  than  that  the  magni- 
fying one  should  be  so  ;  and  the  essential  part  of  his  method 
consists  in  this  : — That  the  rays  which  form  the  illuminating 
image  or  disc  shall  have  their  foci  exactly  on  the  part  of  the 
microscopic  object  to  be  observed,  so  that  the  illuminating 
rays  may  radiate  as  it  were  from  the  object,  as  if  it  were  lumi- 
nous. Now  this  can  only  be  well  attained  by  illuminating 
with  a  single  lens,  or  a  system  of  lenses,  without  spherical  or 
chromatic  aberration,  whose  focal  length,  either  real  or  equiva- 
lent, is  less  than  the  focal  length  of  the  object-glass  of  the 
microscope.  The  smaller  the  focal  length  of  the  illuminating 
lens,  or  system  of  lenses,  the  more  completely  do  we  secure 
the  condition  that  the  illuminating  rays  shall  not  come  to  a 
focus,  either  before  they  reached  the  object,  or  after  they  have 
passed  it. 

MODE  OP  OBTAINING  THE  WHEEL  ANIMALCULE  (Vorti- 
cella  rotatoria). — "  Early  in  the  spring  I  fill  a  three-gallon  jug 
with  pure  rain  water  (not  butt-water,  because  it  contains  the 
larvae  of  the  great  tribe).  This  quantity  more  than  suffices  to 
fill  a  half-pint  mug,  and  to  keep  it  at  the  same  level  during  the 
season.  I  then  tie  up  a  small  portion  of  hay,  about  the  size 
of  the  smallest  joint  of  the  little  finger,  trimming  it  so  that  it 
may  not  occupy  too*  much  room  in  the  mug,  and  place  it  in  the 
water;  or  about  the  same  quantity  of  green  sage  leaves,  also 
tied  and  trimmed.  About  every  ten  days  I  remove  the  de- 
cayed portion  with  a  piece  of  wire,  and  substitute  a  fresh  sup- 
ply. A  much  greater  number  of  animalcules  are  raised  by  the 
sage  leaves;  but  I  have  sometimes  been  obliged  to  discon- 
tinue the  use  of  it,  on  account  of  its  producing  mouldiness.  I 
take  them  out  with  an  ear-picker,  scraping  up  the  sides  of  the 
mug  near  the  surface  (including  the  dirt  which  adheres  to 
them  by  the  tail),  or  under  the  hay  or  sage." — J.  Ford. 

SUBSTITUTE  FOR  THE  CONCAVE  SPECULUM. — Mr.  Gr.  Jack- 
son employs  a  plano-convex  lens  of  about  two  inches  in  diame- 


MISCELLANEOUS     HINTS    TO    M  ICRO  SCOPIS  T  S.    173 

ter,  and  of  four  and  a  half  inches  focus,  silvered  on  the  plane 
side,  and  backed  with  a  plate  of  brass.  This  lens,  when  so 
treated,  becomes  a  reflector  of  about  two  and  a  quarter  inches 
focus,  and  forms  one  of  the  best  instruments  that  can  be  de- 
sired for  throwing  light  upon  an  object  viewed  as  opaque.  We 
have  used  such  an  arrangement  for  some  time  in  place  of  the 
concave  mirror,  and  deemed  it  peculiar  to  ourselves  till  reading 
an  account  of  the  above. 

APPARATUS  TO  PREVENT  THE  EVAPORATION  OF  LIQUIDS 
UNDER  THE  MICROSCOPE. — Vapours  arising  from  the  liquids 
under  observation  would,  by  condensing  on  the  under  surface 
of  the  object-glass,  form  there  round  drops,  which  act  as  so 
many  lenses,  and  which,  arresting  the  rays  of  light  in  their 
progress,  would  scatter  them  in  every  direction,  and  thus  com- 
pletely destroy  the  image  before  it  could  reach  the  object-glass. 
This  effect  takes  place  not  only  when  the  temperature  of  the 
liquid  is  raised  by  the  application  of  heat,  either  directly  or 
in  consequence  of  chemical  action,  but  also  when,  in  studying 
any  body  by  the  microscope,  a  fuming  acid  is  used,  such  as 
the  hydrochloric.  This  inconvenience  is  prevented  by  en- 
closing the  frame  of  the  object-glass  in  a  small  glass  tube,  shut 
at  one  end,  whose  inner  surface  is  closely  applied  to  the  surface 
of  the  object-glass.  This  end  is  then  plunged  into  the  liquid, 
which  is  thus  prevented  from  either  beclouding  the  surface  of 
the  lens  or  finding  its  way  into  the  interior  of  the  microscope 
and  there  producing  the  same  effect. — Raspail's  Organic 
Chemistry. 

DROPPING  TUBES,  for  placing  on  the  object-holder  or  slide 
any  reagent  whose  action  is  to  be  examined,  may  be  easily 
made  by  softening  a  piece  of  glass  tube  in  the  flame  of  a  lamp, 
and  drawing  it  out  till  it  becomes  capillary,  after  which  it  may 
be  broken  to  a  convenient  length.  Fishing-tubes  for  animal- 
culse  may  also  be  made  in  the  same  way. 

15* 


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INDEX. 


A. 

Achromatic  object-glasses,  their  invention  an  epoch  in  histology,  18 

description  of,  34 
Animal  tissues,  to  be  examined  while  fresh,  17 

on  procuring,  73 
Accessory  instruments,  40 
Animalculse  cage,  37,  48 
Asphaltum  cement,  58 
Agate,  64 
Algae,  71 
Aphides,  82 
Acari,  82 

Anatomical  preparations,  85 
Areolar  tissue,  92 
Artificial  star,  as  a  test  object,  99 
Angle  of  aperture,  explained,  100 
Arm  rests,  107 
Albuminous  urine,  144,  157 
Alkaline  salts  in  urine,  147 

Advantage  of  polarized  light  in  examination,  168 
Apparatus  to  prevent  evaporation,  173 

B. 

Bog  iron  ore,  from  infusoria,  14 

Borelli,  his  observations  on  pus,  &c.,  15 

Blood  corpuscles,  85 

Blood  discs  of  siren,  86 

Bone,  86 

Basement  membrane,  92,  93,  116 


184  INDEX. 

Bat's  hair,  102 

Branchial  cartilage  of  tadpole,  120 

Blood  in  urine,  144,  155 

Bile  in  urine,  156 

Brewster's  mode  of  illuminating  objects,  171 

C. 

Causes  of  error  in  observation,  15 
Coal  beds,  from  vegetation,  14 
Coddington  lens,  29 
Compound  microscope,  31 

defects  of  the  common,  33 

improvements  in  the,  33 

mechanical  conveniences  necessary  to  the,  35 

forms  of  the,  35 

most  celebrated  makers  of  the,  36,  38 

Smith  and  Beck's,  36 

efforts  to  reduce  the  price  of  the,  38 
Condenser,  37,  40,  49,  50 
Condensing  (or  bull's-eye)  lens,  37,  42,  50 
Camera  lucida,  37,  45 
Compressorium,  48 
Cook's  preserving  fluid,  54 
Cooper's  preserving  fluid,  54 
Chloroform  as  a  preservative,  56 
Cells  for  mounting,  58 
Cements,  58  » 

Canada  balsam  cement,  59 
Charring  vegetable  matters,  59 
Carbonate  of  lime,  64 
Crystallization  of  salts,  64 
water,  65 
Cuticles,  66 
Cellular  tissues,  67 
Charcoal,  69 

Circulation  in  vegetables,  72 
Corals,  78 
Circulation  of  blood,  86 


INDEX.  185 


Capillaries,  their  functions,  95 

of  skin,  89 

of  mucous  membrane,  94 
Crystalline  lens  in  fish,  90 
Ciliary  processes  of  the  eye,  90 

movement,  94 
Chromatic  aberration,  33 

mode  of  observing,  98 
Circulatory  system  of  insects,  112 
Chemical  constitution  of  organized  bodies,  115 
Cell-growth  in  a  meliceritous  tumour,  121 
Classification  of  animal  tissues,  121 

malignant  growths,  127 
Carcinoma,  129 

Chemico-gelatinous  injection  by  Dr.  Goadby,  139 
Cystine  in  urine,  153 
Colours  exhibited  by  polarized  light,  166 
Cleaning  the  glasses  of  microscopes,  170 
Cabinet  for  microscopic  objects,  171 

D. 

Dissecting  microscope  of  Mr.  Slack,  27 
Dark  wells,  37 
Diaphragm,  37,  40,  49,  51 
Deut-ioduret  of  mercury,  65 
Dissecting  needles,  106 
troughs,  106 

Digestive  system  of  insects,  111 
Development  of  cells,  116 

animal  tissues,  119 
Diabetic  urine,  144,  157 

E. 

Erector,  36,  42 

Entozoon  folliculorum,  82 

Epithelium,  92,  93 

Examination  of  morbid  structure,  124 

its  importance,  126 


186  INDEX. 

Encephaloid,  131 

Earthy  phosphates  in  urine,  143,  148,  159 

Eyes  of  animals,  90 

F. 

Fossil  remains  determined  by  the  microscope,  14 

Fontana,  histological  observations  of,  17 

Frog  plate,  46 

Fishing  tubes,  48,  173 

Fossil  wood,  69 

Ferns,  71 

Fibrous  and  areolar  tissue,  92 

Forms  of  nuclei,  118 

Form  of  fibrous  tumour,  127 

G. 

Geology,  use  of  microscope  in,  13 
Goadby's  fluids,  55 
Gum  mastich  cement,  59 
Gannal  process,  54 
Glycerine,  54 

H. 

Histology,  created  by  the  microscope,  14 

Hewson  on  the  blood  globules,  17 

Herschell's  doublets,  29 

Holland's  triplet,  31, 

Huygenian  eye-piece,  34 

Hairs,  down,  &c.,  of  plants,  69 

Hard  tissues,  71 

Hair  of  animals,  85 

Horn,  hoofs,  quills,  &c.,  85 

Human  blood,  86 

Hair  of  Dermestes,  102 

Hippuric  acid,  146 

I. 

Importance  of  the  microscope  to  zoology,  14 
Inorganic  objects,  64 


INDEX.  187 


Illuminating  lamp,  43,  50 
Iron  pyrites,  65 
Infusoria,  classification  of,  74 
on  procuring,  75 
to  observe  the  structure  of,  77 
fossil,  77 
Insects,  antennae  of,  78 

eggs,  79 

elytra,  79 

eyes,  80 

feet,  81 

hairs,  81 

mouths,  &c.,  81 

parasitic,  82 

trachea,  83 

stings,  ovipositors,  &c.,  83 

internal  anatomy  of,  109 
Injected  papillse  of  skin,  90 

preparations,  94 

Instruments  for  minute  dissection,  105 
Internal  anatomy  of  insects,  109 
Injecting  materials,  134,  137,  138,  141 
Instrument  for  diagnosis  of  tumours,  133 
Injection  of  the  lymphatics,  142 

J. 

Japanner's  gold  size,  58 

K. 
Kiestein,  144 

L. 

Lenses,  different  forms  and  effects  of,  22 
simple  mode  of  making,  28 
imperfections  in,  29 

Lewenhoeck,  his  discoveries,  16 

Lieberkuhn,  his  anatomical  researches,  17 
concave  reflector,  so  called,  44 

Lamp-black  cement,  59 


188  INDEX. 

Lichens  and  fungi,  72 
Loaded  corks,  106 
Lepisma  saccharina,  103 

M. 

Malpighi,  microscopic  researches  of,  15 
Modern  observers,  19 

Medico-legal  inquiries  with  the  microscope,  21 
Micrometer  eye-piece,  35 
Magnifying  powers,  hints  respecting,  49 
table  of,  23 

to  obtain  the  power  of  a  compound  microscope,  40 
Mirror,  use  of  the,  50 
Management  of  the  light,  50 
Mounting  transparent  objects,  53 

in  the  dry  way,  53,  54,  61 
in  fluid,  57 
in  balsam,  59 
Marine  glue,  58 

Mounting  cellular  structures,  60 
opaque  objects,  61 
crystals  for  polarized  light,  63,  168 
Mosses,  71 
Muscular  fibre,  91 
Mucous  membrane,  92,  93 
Mouse  hair,  102 
Morpho  Menelaus,  1*03 
Muscular  system  of  insects,  113 
Morphology  of  pathological  fluids,  133,  174 
Method  of  injection,  by  Ruysch,  138 
Ranby,  138 
Monro,  138 

Professor  Breschet,  138 
M.  Doyere,  139 
Dr.  Goddard,  141 
Mucus  in  urine,  155 

N. 
Nervous  structure,  examination  of,  91 


INDEX.  189 


Nerves  and  capillaries  of  muscle,  91 
Nervous  system  of  insects,  112 

0. 

Organic  remains  in  limestone,  14 
Optical  illusion  to  be  guarded  against,  17 
Opaque  objects,  mounting  of,  61 

how  viewed,  51,  52 

Mr.  Brooke's  mode  of  viewing,  45 
Oolites,  65 
Organic  fibres,  72 
Oxalate  of  lime  in  urine,  143,  150,  159 

P. 

Polarizing  apparatus,  41 

Preparation  of  glass  slides,  54,  57 

Preserving  fluids,  54 

Pollen,  69 

Pigment  cells  of  skin,  89 

of  the  eye,  90 
Pontia  brassica,  104 
Podura  plumbea,  104 
Proximate  principles,  115 
Primary  form  of  org.-uiic  matter,  115 
Pus  in  urine,  144,  155 

distinction  between  it  and  mucus,  125 
Polarization  of  light,  162 


Qualifications  of  a  microscopist,  18 

R. 

Religious  sentiment,  microscope  conducive  to,  13 
Reflecting  microscope  superseded,  38 

a  curious  form  of,  38 
Rules  for  microscopic  observations,  49 
Raphides,  71 
Retina  of  the  eye,  90 
Respiratory  system  of  insects,  109 


190  INDEX. 


S. 

Simple  microscopes,  construction  of,  23 

magnifying  powers  of,  23 

mode  of  mounting,  23 

form  of,  for  opaque  objects,  26 

Stanhope  lens,  29 

Silver  cup  or  Lieberkuhn,  37,  44 

Side  reflector,  37,  44 

Stage  micrometer,  46 

Size  of  glass  for  mounting,  53 

Sealing-wax  varnish,  58 

Sand,  65 

Sections  of  granite,  &c.,  65 
coal,  65 
wood,  68 

Siliceous  cuticles,  &c.,  69 

Starch,  70 

Seeds,  71 

Sponges,  78 

Shells  of  mollusca,  83 

Scales  of  fish,  84 

Skin,  89 

Spherical  aberration,  33,  99 

Scales  of  insects,  103 

Shells  of  infusoria,  104 

Swammerdam's  scissors,  105 

mode  of  dissection,  107 

Secondary  organic  compounds,  115 

Scrofulous  growths,  127 

Syringe  for  minute  injection,  135 

Stopping  false  light  in  microscopes,  170 

Substitute  for  the  concave  speculum,  172 

T. 

Trough  for  chara,  &c.,  36,  48 
Thin  cells  for  delicate  tissues,  57 
Teeth,  88 


INDEX.  191 


Theory  of  life  and  sensation,  96 

Test  objects,  Dr.  Goring's  discovery  of,  98 

character  of,  102 
Tinea  vestianella,  103 
Tables  for  examination  of  urinary  deposits,  159 

of  results  of  Dr.  Gruby's  observations,  174 

U. 

Utility  of  the  microscope  in  medicine,  19 

Urinary  deposits,  143 

Urea,  145 

Uric  acid,  143,  145,  159 

V. 

Vegetable  physiology,  microscope  indispensable  in,  14 

Varley's  dark  chamber,  41 

Vegetable  tissues,  dissection  of,  66 

Vascular  tissue  in  plants,  67 

Vitality  and  electricity  not  identical,  96 

Valentin's  knife,  106 

Vital  principle,  theories  respecting  the,  96, 114 

W. 

Withering's  Botanical  Microscope,  33 
Wilson's  Pocket  Microscope,  24 
Wollaston's  doublet,  30 

condenser,  41 
Watch-glasses  useful,  48 
White  fibrous  tissue,  92 
Wheel  animalculae,  mode  of  obtaining,  172 

Y. 

Yellow  fibrous  tissue,  92 

Z. 

Zoophytes,  78 


No.  48  CHESTNUT  STREE 

Have  for  Sale  a  very  large  Assortment 

COMPOUND     MICROSCOPES. 

Neatly  mounted  in  Brass,  of  a  power  ranging  from  15  to  60  dia- 
meters, from  $2  50  to' $10 

An  Achromatic  Microscope,  cylinder  brass  body,  with  rack-work 
and  condenser — power  50  times.  Price,  $16  00 

Ditto,  with  power  of  120  to  135  times,  $22  and  $23 

A  still  better  Microscope,  also  Achromatic,  to  screw  upon  top  of 
the  box,  which  makes  it  firmer — large  stage,  rack-work,  con- 
denser, dissecting  instruments,  &c. — power  120  times.  Price,  $26  00 

The  same  Instrument,  with  extra  Lenses,  so  as  to  increase  the 
power  from  160  to  250  times.  Price,  $33  00  to  $37  00 

The  very  best  Achromatic  Microscopes,  with  movable  lever  or 
rack-work  stage — Microscope  to  be  placed  either  vertical  or 
horizontal — bull's  eye  condenser — frog  plate,  &c. ;  cost  from 

$150  to  $650 

Sets  of  Achromatic  Lenses,  of  various  powers,  separate  from  the 
Microscopes,  $4  50  to  $9  00  per  set. 

Eye-pieces,  of  various  powers,  separate  from  the  Microscopes, 

$2  25  to  $3  00  each. 

Glass  slips  for  Microscopic  slides  or  preparations,        50  cts.  per  doz. 

Glass  dishes  and  covers  for  Microscopic  slides,  and  wet  prepara- 
tions, $1  25  to  $3  00  per  doz. 

Thin  glass  for  covering  Microscopic  objects. 

Microscopic  sliders,  in  sets  of  12,  24,  and  36,  of  portions  of  in- 
sects, sections  of  wood,  guano,  feathers,  &c.  Prices  from 

$2  to  $6  50  the  set. 

Finely  prepared  objects,  parts  of  insects,  &c.,       19  to  50  cents  each. 

"  "  "        anatomical  as  injections,  75  cents  each. 

Also,  Magnifying  Glasses  in  horn  cases,  for  the  pocket ;  Microscopes 

to    examine    the   ear ;     Urinometers.    Thermometers,    Hydrometers, 

Weighing  Scales,  Magnets,  Mathematical  Instruments,  Spy-Glasses; 

Camera  Lueidns,  Stanhope  Lenses.  &e. 


11111 


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